Is my mortgage safe? Has my flat value decreased?

I'm amazingly ignorant here because I'm new to the UK and have been away for over a year. But here in California foreclosures are epidemic due to "balloon mortgages" (low introductory rate, then much higher rate). We have a flat in Scotland with a mortgage like that. Is our flat worthless? How do I find the current value? Is there the same problem in the UK with foreclosures; is the housing market plummeting here too?