Hello Britgirl,
I am going through the same post-grad issue, so I can relate... I already hold a Masters and am completing another, both here in Australia. I am moving to the UK in July with 8 subjects to go and my wife has 3, we have been able to continue to completion our Australian studies as Australians and without affecting our study benefits. It is straightforward to organise exam adjudication overseas.
As far as the UK is concerned, there is a 3 year waiting period before (as a UK resident or citizen) you are entitled to access UK student funding or loans if you have lived overseas for more than 3 years, this includes children moving from secondary to tertiary.
Hope that helps