I would look at the 785g boards which have plenty of reviews and come with onboard graphics. There is an MSI Am3 at scan for (~£50 but is on back order). DDR2 and DDR3 look to be about the same price atm;
Budget DDR3 for £64 leaving about £85 for the CPU.
There are a slew of new tri and quad core athlonIIs out there and some energy efficient models too which may be worth investigating. A tricore is only £7 more at scan. I warn you the stock cooler will probably be horrible and I am sure it is teh same one that came with my S939 3200+. Check compatibility with the mobo vendors website for wattage and processor support (and the memory too!).