Hi Chrissie, welcome to the forum
I presume you're talking about
this camera?
Sadly, all compacts will struggle when the ISO is pushed up (usually above 400 or so). The compacts with the best low light performance at the moment (and they will be nowhere near your EOS 450D) are the
Sony WX1 which is about £230, the
Fuji F200 EXR which is £160, the
Canon Powershot S90 (£310) or the
Canon Powershot G11 which is a whopping £420.
It may also be worth considering the
Canon Powershot SX210 IS which is a decent all rounder for £230.
The Fuji EXR cameras are pretty good in low light (for compact sized sensors) as they use a special pixel binning technique when shooting at high ISOs which means you get less noise but a smaller (lower resolution) image. It works though.
I know it's not a huge amount of help but it's difficult to know what your expectations are! You would probably be better off spending £100 (less normally) on a 50mm f/1.8 for your 450 and using that!