For the graphics card see my thread on what your money will buy you
http://forums.hexus.net/graphics-car...-x-thread.html (newly stickied
) I would consider the 4830 for £95 (check eBuyer for a good price as Microdirect are out of stock) they overclock easily to 4850 speeds obviously 4850s OC as well though to go faster! And with the P45 board you can add another later if you want crossfire goodness. If the extra £20 is there to spend then the 4850 is really the best card available in the £90-£120 bracket.
As for PSU I'm with Mike a decent 425W+ PSU will do you fine and the Enermax is well priced if you want more power then still look at the Enermax the Corsair has been priced to high now in my opinion. From Blitzen's accounts the Enermax is the superior unit when the was £15 difference the Corsair was easy to recommend now with only a couple of pounds difference its a lot harder.