On your budget of £70, providing your not interested In running 2 graphics cards, take a look at the Asus P5Q. That's a lot of board for the money
has an Intel P45 chipset, it's available now, will handle your 4 GB RAM and seems to be well reviewed by those who've bought one.
http://uk.asus.com/products.aspx?l1=...64&modelmenu=1