Hi there,
Not 100% sure about your exact status and what that all means in terms of conditions for getting a mortgage.
With the financial side of things in deep mire, the mortgages market has shrunk substantially, no more silly 100% or even more stupid 125% mortgages and the 5 or 10 % deposit mortgages only going to those with impeccable credit histories at the moment - I'd say pretty much anyone who's from abroad and with no (current) permanent right to stay would be handled under the foreign buyers umbrella within mortgage providers selection criteria.
I think you'd probably need to get together more than a 25% deposit in order to get more competitive mortgage rates and deals. 25% is a figure touted around for UK citizens to make and put down if they want to puchase - so foriegn buyers would I'd estmiate need 35-40%.
Remember, interest rates are currently very very low, but they WILL GO UP again once the economy stabilises and starts to return to better health, you MUST make sure that any budgets you have will allow for these increases if for instance you manage to get a tracker. If you get a discount rate now, then at the end of the 1,2,3,4 or 5 year fixed term, be prepared to pay the increased level of re-payments if the interest rates are higher then. Find an indepedant mortgage advisor who can crunch some numbers based on your actual income levels and much more importantly, the amount of disposable income you have each month to assess your suitability for any mortgages he may have to sell to you.
Good luck! Cheers! DtM! West London & Slough UK!