I'm looking for day or weekend returns

I'm told it's the company sites that give the best deals but they seem to only start from the UK

We book P&0 via the website for Calais - Dover...

Which place will be your journey point? Pls. mention the route for which you want info.on ferry services?

You need to be specific about the routes you want to travel by. There are so many websites available providing complete info. on cross Channel ferries from and to the UK. You just need to visit any of these and give the source and destination ports of your trip and they will return you with the desired routes and ferry companies operating on these routes along with all other relevant info.

Leaving from Diepe or LeHavre, but Calais ,Dunkirk etc would be OK and more likely to have day returns.

All the websites I have tried either give standard fares or their weekend and day returns start in the UK.

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All the websites I have tried either give standard fares or their weekend and day returns start in the UK.
Have sent you a PM

You might need to book the France /UK leg from within France.
This will appear online to the system that you are in France and you will be treated as french.
It is also worth comparing the £ vs euro prices.

Cyrian

Did you have a look at
www.ferryfaresto.co.uk/
It used to be
www.ferryoffers.co.uk/