the research councils, worried about having to pay some money to other EU nationals, introduced this requirement to avoid other EU nationals en masse being able to claim funding. at the same time they created bureaucratic difficulties because OF COURSE they did not mean to make brits who went abroad for a while uneligible, so they had to include lots of complicated exceptions. are you paying "home" fees (rather than "home/EU","overseas")? then you should be eligible. the intention of the rulings is clearly that you should be eligible. the wording is less clear. you need to talk to the registrar at your uni. explain your situation in detail (from when to when you were in Britain, when you were abroad, for how long, with what intentions, do you have family in Britain, did they stay when you left, is the rest of your family also British & in Britain, etc). there is no general way to find out - just your particular case which you need to make.