Hi OP - reading this with interest as we moved overseas last year.
Out of interest, where ru moving from? Do you really need to move 'back'? As you've been away for so long, surely the new country is 'home' now?
I'd agree with PPs re costs - I'd estimate around £10,000 shipping costs (across the Atlantic for us, cargo ship, 6 weeks, contents of a 2 bed) and around the same again in terms of start up costs: £2000 first month's rent, £2000 security deposit, £2000 furniture, £2000 paperwork/visas etc, £2000 car deposit. You'll need access to savings or some other source of income to fund this alone.
Personally, we don't find the US (East Coast) any cheaper than the UK, but costs are distributed differently, so eg car/petrol cheaper but mobile contracts a lot more for a lot less. Again though, not sure where you're moving from so this may be irrelevant. You really need to break down what you need from what you want.
Having lived in London before here, £40,000 really isn't a lot given the cost of housing. It would be fine elsewhere in the country but anyone not having bought before 2008/Lehman collapse is likely to have a huge mortgage/rent.
It may also help you to come over to the Living Overseas thread where there are loads of people who've moved back and forth over the years so they may also have some good advice.