You're getting a q6600, I hope you plan on overclocking it! Those things are practically made for overclocking
For a motherboard, if you don't intend to SLi in future, I'd say go for the Asus P5K Premium WiFi-AP. It got a good review in Custom PC magazine, and they're pretty tough in their reviews. It's got lots of features , supports DDR2 (MUCH cheaper and almost identical performance-wise as DDR3) and will be very comfortable ensuring that your g0 q6600 shows its true colours (speed-wise). On the other hand, I've got an eVGA 680i motherboard and have been happy with it, my q6600 is running at 3ghz without any problems at all. I'm sure I could get it higher if I spent some time on it. But I went the nvidia route because I wanted SLi.
In terms of graphics cards, the Geforce 9800 GTX came out yesterday. It's faster than the 8800 GTX, the 8800 GTS and even the 8800 Ultra in some circumstances. It's not truly a 'next-gen' card performance wise (as the naming scheme suggests) but it costs £213 @ YoYo so hardly more than the GTS. Plus, it'll probably maintain it's value longer in case you want to resell it down the road to upgrade to the possibly much faster 9900-series cards that are possibly coming out this summer, or the rv770 series if ATI/AMD get their act together.
I realise that you also want to see if you can save some money and my suggestions so far have all been for higher-performance (although at decent price/performance ratio) components. Well if you want to save money, don't get a 8800GTS/9800GTX and instead get a 8800GT or 9600GT. This is especially if you game on a smaller screen (lower than 1680x1050 which is 20"/22" widescreen monitors). The smaller the screen, the smaller the gains you get from having the faster graphics cards. With the 8800GT/9600GT you'll still be able to play games like CoD4, TF2, World in Conflict etc. at decent settings with good framerates. The graphics card that is the best bang per buck (bang per pound?
) is very dependent on what screen size/resolution you have.
Another measure you could take to save costs is to go for a 1.6GHz dual-core pentium E2140. I know you'll probably cringe when I say pentium but that chip is different from the Pentium D's. It's more or less a Core 2 CPU. However, it is
only worthwhile to get it if you're willing to overclock. It shouldn't be too difficult to get it to 3GHz or more, especially with the M0 version (as opposed to L2). Particularly if you go for a good quality motherboard like the Asus. The E2140 costs about 40 quid!
If saving money isn't a huge priority though, definitely go with the q6600!