I moved to the UK for work 10 years ago.
Not London. Salary over 6 figures, housing allowance lump sum (still in a recession then so the package would have looked MUCH better a year or 2 prior), paid for my visas, air shipment of all of my belongings (not car), relocation of my pets (over $3k), 5 extra days holiday per year on top of the 28 days per year for travelling back home. $2,500 per person for flights back home, and a $20,000 “disruption bonus”. One month corporate housing and rental car. Services to assist in finding a rental home, schools (if I had had kids), doctor, etc.
And the one item that should ALWAYS be standard, someone to do both your US and UK taxes.
£40k is entry level pay for a project manager.
What is it that makes you want to move? Not going to lie, living abroad is the same as living at home. Just different things to see and do. But those can easily be seen and done on holiday.
I never planned to live here forever (moves here single, now married with kids). I really REALLY wish I had family support when it’s been needed. I have wonderful friends. But no one can replace family.