The official info is here
We were overseas for 16 years as ex-pats and only returned to the UK two years before our eldest DC was due to start Uni. We figured that if we couldn't get home fee status for her we would either pay the overseas rate or get her to take a gap year. She decided to study medicine so the overseas rate would have been ridiculous and it is extremely hard to get a place at medical school as a foreign student as there are quotas restricting the numbers of non UK students. She also preferred not to take a gap year.
Our situation was not clear cut, we did not own a house in the UK and in our last country paid local taxes. We did come back to the UK at least once a year and my husbands contract/pension etc was Uk based. Also, we were paid as expats and got our houses, cars,schooling etc and flights home paid for.
What we discovered is that each Uni can interpret the Rules differently and that some Uni's will not confirm whether or not you will get Home Fee Status until after you have accepted a place 
Fortunately, it all came together perfectly and my DD got into her first choice Uni which happened to be the most helpful with regards to clarifying my DD's fee status. They went through all our paperwork before we applied and confirmed that we should be OK.
The best advice is to keep a property in the UK, maintain UK bank accounts, visit regularly (and keep proof) make sure your work contracts are UK based and clearly 'ex-pat' contracts and to keep an eye on the ever changing legislation.
It's crazy that each Uni decides how to interpret the rules themselves. One of the Uni representatives said it was not that unusual for two different Uni's to give a student a different fee status 