Computers for kids

[doyourworst]

I want to buy a tower/desktop pc for my kids birthdays. It will be theirs as I have my own laptop. They are only 6 and 4 so they will only be using it for cbeebies and cbbc type websites for now, maybe a bit of homework stuff for my 6 yo. I think I'll only need a fairly basic one, not big on memory but maybe a fair amount of processing power for graphics/games. Can anyone recommend anything? I don't want to spend a massive amount, was thinking somewhere between 150-200 max.

I think (if you can streach to 250) this may be good option:
www.argos.co.uk/static/Product/partNumber/273969.htm

This is British company, I used to own one of those and had no problems with it. Admittedly is a bit loud but was working perfectly.
I am assuming here that you have monitor.

Otherwise you can buy second hand, but I don't know which would be reputable place to source that.

Thanks for the suggestions. The getonline@home recommendation is particularly interesting, thanks CorusKate.

:)