best Ixus you can afford, I'd find an extra 25 quid or so as it puts you in a bette market segment.
You're the reason Cannon get away with charging extra for compacts that are not as good as their competition! That Samsung I mentioned above utterly demolishes anything at it's price range.
Samsung build quality is pretty questionable in their compact range <£100. I can't speak for that specific model, but we used to find consistent faults with most of their cheaper models. Unfortunately, panasonic have gone downhill in their budget range, but for £100 they still have some decent offerings. And, as much as Canon do price gouge a bit, their cameras are well made.