Thank you - I don't think that really answers my question - I should have made it clear that neither our property in the UK or the USA is (or will) be rented - i.e. neither will generate income.
Whilst I understand your point about US tax rates being more attractive than UK rates, as it happens ALL our UK investments are held in either ISA or Personal Pension funds - in short we have very little 'taxable' income and have structured things to ensure we are now both basic rate taxpayers. Because of that it seems to me that we would actually be better keeping our residency here in the UK - which will allow us to maintain the benefit of the tax free ISA accounts and the relatively attractive income options which we will be able to take from the Pension accounts wef April?
In short what I really want to understand is: if we had Green Cards and remained UK residents (simply using the GC's to spend more than 6 months at a time in USA - should we wish to), whilst understanding we will have to file a US tax return to show our income and capital gains in UK, am I correct in thinking that despite filing the US return, in practice we would not actually have to pay anything in the USA because the double taxation treaty with the UK (where any tax would have already been paid) would effectively leave us with a nil to pay balance?
OK - many thanks