British Expats - Registering my Vespa in Italy

You've been given some excellent advise already.
When I hear or read of those wishing to register a 'foreign' vehicle in Italy, I shudder. I've done it twice several years ago and it was a nightmare scenario.
Here's my sad saga:
My overseas posting at the time was reassigned to Italy, I had a company owned vehicle, plus my personal 'toy'.
Weeks prior to departure I'd contacted our HR department in UK for their blessing to sell the company-owned vehicle in Spain where I was at the time. I knew this had to make sense, but in their 'wisdom' - and I use that word sparingly - they decided I should drive to Italy with the vehicle together with our personal belongings. I argued the case, they disagreed, so as they were calling the shots I had to concede. On reflection, the only benefit was that we could transport more of our personal effects to be readily available on arrival. Our remaining personal effects shipped seperately took over a month to arrive.
My wife then drove the company owned vehicle (a Renault 18 manufactured in Spain as a Renault Fasa) from Madrid to Milan. I followed behind in my own car.
To cut an extremely long story as short as possible (and also retain some interest), getting that vehicle legally onto the Italian system was a nightmare.
One of the initial problems was the car's manufacturing origin as a Fasa Renault, which wasn't recognised in Italy, but eventually overcome when I contacted Renault in Paris Boulogne-Billancourt, who for a very modest sum sent me a duplicate of the original constructors certificate - which was acceptable.
That was the first major hurdle which took several months to resolve, but I was hardly off the starting blocks! Official translation of documents from Spanish to Italian, and also French/Italian were required. Worse still, as the vehicle hadn't been registered for importation when we crossed the border, that required a fairly long drive down to Genoa with an excellent newly-aquainted Italian 'translator', who not only linguisticaly but also culturally knew exactly which hand to 'pass under the table' and with how many lira etc. Also at the same time for convenience we made a detour to the Ligurian Riviera. For info, Finale Ligure is a glorious location, especially the small hamlets along the coastline and in the surrounding hills - not to mention the many small, delightful restaurants.
To show my appreciation to my worth-his weight-in-gold 'translator', and also to compensate for my own inconvenience, I made the journey to the coast an official business trip with a 3-night hotel stay, together with the liaison visit to Piaggio at Finale Ligure who was one of our aviation-related sub-contractors. That was a truly memorable trip, plus I'd obtained the officially stamped importation document.
Months later after several other difficulties (changes in government resulting in subtle changes to the official documents required) I received the date to arrive at the officine revisione for the vehicle roadworthiness checks (already having paid a local garage to have headlights + indicators checked and corrected).
The final, almost knockout blow occured just after passing all the obvious roadworthiness checks, and also close scrutiny of all documentation, I arrived where the last inspector was standing at the 'chequered flag' holding a clipboard. He made a number of ticks in corresponding boxes, and then finally leaned over very closely with eyes fixed on the edge of the windscreen. Then like a death sentence, he suddenly marked a large X on his clipboard!
A few moments of badly pronounced expletives and hand gesticulating later, I understood (not without difficulty) that the windscreen construction was of hardened glass and not laminated as required. The vehicle had clearly fallen at the last hurdle!
Frankly at that point I was tempted to drive the car into a nearby lake, but unfortunately was obliged to continue on this frustrating, and already frighteningly expensive excercise.
A month later, plus more lira and the windcreen was changed. I then had to wait for yet another officine revisione appointment, which fortunately was successful. More appointments and visits (with my translator) to obtain the Italian registration document plus the new number plates, plus more lira and I was home and dry.
I hasten to add that the pile of receipts and other paperwork for official documentation which included replacement parts (new windscreen etc) road trip mileage, hotel and restaurant receipts were all readily accepted 'back at base' when submitted. I also added a scribbled note to the effect that these significant expenses could have been avoided if my original recommendation to sell the vehicle had been heeded. This was received without further comment.

Regarding my own vehicle, an Alfa Romeo 2lt Spider Veloce - purchased in France and registered there, I hadn't initially planned re-registering in Italy, but as my posting was extended and having being stopped twice by the Carabinieri and advised that registration was necessary I thought it wise to comply. My very good friend Giuseppe the 'translator' was more than happy to assist me a 2nd time, and we followed a somewhat simplified procedure as the vehicle was at least of Italian origin. Although there was less bureaucratic hassle the procedure was still rather daunting, even with my colleague knowing which strings to pull and which palms to cross with the correct amount of lira. The total expenditure for that re-registration was far less, fortunately so as it came from my own personal funds.
It was some time later that I realised that my colleague (by this time a very good friend) was not an official translator, although he did have an accredited translator's stamp which - although I never asked - was no doubt hooky.
My advise to anyone tempted to import a vehicle and bring onto the Italian register is, "Don't even think about it!"

And believe it or not, one year later I received a telex (remember those?) from HR head office stating that their recent accounting showed there was an access of funds still allocated to my Italian posting, and as the company vehicle, quote "is already 4 years old", I was requested to change it and purchase new locally! My head was still shaking in disbelief on arrival at the local Milan Alfa concessionaire.......