My best friend has just asked my advice on this, and my instinct is to say not in a million years, as economic conditions are so unpredictable.
However, BBC news has a story today suggesting that if interest rates do anything, they'll fall, which will benefit someone on a variable rate.
I'm still dubious, as they'd be stretching themselves a bit with this rate (although they could cover a couple of percent increase in interest rates without monstrous drama). They can't get a fixed as they have less than perfect credit records.
Incidentally, I am glossing over my general horror at someone contemplating buying a house at the moment when they don't have to, and plan on selling (at a profit) in 3-5 years, but that's another story. If anyone has a polite way of phrasing 'are you out of your mind' I'd be interested to hear it!