if its only £80, then great go for it. But those things are very iffy when it comes to motherboard, cant remember if your dfi lanparty works with the newarksl, best to check this.
also if you cant get 3ghz, how about 2.8ghz from a 3700+ 754, they are good chips and you might be able to get one from auction for about the same price, or try the members market wanted section.
i have another idea for upgrade, you could get a the E6300 conroe and one of those asrock motherboard, which works with ddr1 and its agp, its only 32 pounds. that could be another option which wont set you back more than 150. obviously its not as fast as full ddr2, but its not that much slower either and it saves you buying yourself ddr2 ram, and you could always sell some of your gear to recoup some of the cost