You might be able to build a system for about £350 based on a home PC and a cambridge or logitech 5.1 digital sound system.
You could build a PC around a (less than £70) LG HDDVD?Blu-Ray/DVD & CD RW drive for about £250 if you shopped around and you should be about to find a matching 5.1 speaker system for about £100.
If you already have a desktop PC you're most of the way there already, and you can use any remainder to buy quieter fans and other components (if necessary).
Whatever you do, it's going to be cheaper, will sound better, and much more versatile than a standard stand alone BD player with speakers.
That's what I've done, and it really works very well indeed. Build one around a M-ITX motherboard with built in networking, sound card and you can get a really classy enclosure to suit your own tastes.