When you all moved to the US, who did you have to tell, I know about banks and utilities mortgage etc... but are there people who could be overlooked? I was told about HMRC but did anyone leave without telling them? I have heard of people leaving to live in Europe without telling the world and his dog, but is there any difference? any advice welcome.

Inform HMRC as you may be entitled to a tax refund. Other than that, I don't think I informed any other entity.

I agree with this. The details are here: https://www.gov.uk/tax-right-retire-abroad-return-to-uk

Not something you have to do but having your mail re-directed is well worthwhile. I avoided some major identity theft attempts as a result of having my mail re-directed.

Thanks so much for your advice, its all very overwhelming and we didn't want to forget or just overlook something.

How long before you left did you tell HMRC etc?

It would be polite to inform parents/children/spouse/etc that one is moving.

Darn it, I thought I'd get away without them noticing I had gone, at least until they realised I hadn't washed so they had no pants to wear...

HMRC? Immediately, so I could get my surplus PAYE back.