Soldato
This is certainly one of my worries as a FTB. We're going with a 2 year fix with overpayments, so the house would need to be worth circa 16% less than what we bought it for to end up in negative equity. I have absolutely no idea if that's realistic or not, as I don't have a crystal ball, nor am I an economist, but that seems like a catastrophic drop in value over a 2 year period. Reading something like that makes me feel anxious about buying now.
HSBC provided an example of what the monthly mortgage payment would be after moving onto the SVR at today's rate and it increased by approximately £100. We could afford that. We could even afford it if the payment increased by £500.
Don't be terribly put off by my words, I just highlighted a potential scenario because a lot of people seem ignorant of that possibility.
In your case the SVR seems manageable so you should never wind up in serious trouble, although job security and ability to pay the mortgage is a factor that we all contend with.
SVR rates are more of a problem with very large mortgage balances, I can only surmise that with a £100 increase your mortgage isn't massive.