I tried to get a mortgage when I was a Ph.D. student. I had been in the country for nearly 4 years at the time, had a provable income and a large deposit, could provide a guarantor (but she was outside the UK, so didn't count) and this was during the time when anybody and their dog could get a mortgage. I asked at several banks and they didn't even bother to check their systems, they just said no. Now, when credit is much harder to get, I would say there is no chance.