Hey kowenicki, congrats on the PS3!
Listen to these other guys about the HDMI wire. I got a Monster cable that was retailing for $70. Big ripoff. I got lucky, though, because I was getting an HDTV at the same time, so it got thrown in for free. But shop around. I saw some cheap ones on Amazon a while back if you can't get monoprice to ship to the UK(though, I don't see why they wouldn't .)
As for the keyboard, I don't yet have a wireless keyboard. Whenever I need a keyboard, I bring home the one from work. It's USB, though. I'm definitely going to start looking, though, as typing these posts with the Sixaxis is probably going to drive me mad!
Oh, and about Singstar, I've mentioned this to another new PS3 owner with a daughter as well, please be careful with the online video submissions. There's a feature on Singstar where you can upload vid clips of your karaoke to the community for viewing and rating akin to YouTube. Like most online communities, some of the content could be inappropriate for kids depending on their maturity level. 99% of the vids are probably fine, but some might be a bit over the edge. It is great fun to see and laugh with/at alot of those vids, though. Some people go all out with costumes and everything.
I left my game recs on your page a little while ago. Hope to see ya on PSN sometime!
I'll hit you up for some advice when I first adopt a 360 into my home. :)