Thanks Blencogo. I had checked that - they are off. Oddly though, when I went to 'double check' it on seeing your reply, when I played with setting timing on repeat keys, if I tried it out in the 'test' box, keys held down do repeat. But they still don't when I'm typing anywhere else 
The Vaio is VPCEH1L8E and I'm using Windows 7. I've had both for some time and this problem has only just started.