As we have been out of the UK for 16 years will we be able to sign up for a mobile phone plan or will we have to get PAYG package? I seem to remember mention of the latter being the only option due to a lack of credit history but I'm hoping I've got that wrong.
Best companies to go with, who to avoid like the plague, what to watch out for etc, etc. Thanks.

No idea if you would be able to get a mobile phone contract, but if you can't then have a look at somewhere like Music Magpie for handsets, they're great, and then just do a SIM only deal. I always do that anyway to save money - currently paying £10 a month for 30GB and unlimited calls/texts.

GiffGaff have some good PAYG deals: https://www.giffgaff.com/sim-only-deals

might be best going PAYG for a while anyway as depending where you live some networks have a VERY poor signal so would be a shame to sign up for a contract and find you can't actually use it (where I live anything other than EE has signal issues!)

Cheers all. Feeling really daunted by absolutely everything at the moment. Some good advice DerekB. Whereabouts are you in the country?

I'm in a village called Wynyard up in the North East

I'm just south of you in Guisborough

I had a choice I could either use my dads address (we stayed with him when we first arrived) and “go on a plan” but I decided to buy my own phone and PAYG as the offers were fab (still are) and no contract which I much prefer, we had no credit history either but we found it very easy.

My cousin provided us with 2 Giffgaff sims which was great. So we are on a rolling PAYG plan with them for now. It's certainly much cheaper than our NZ plan and for double the GB that we had in NZ!