It will be 4-5 years before SB or bulldozer get under £100 for a CPU & board
Highly unlikely. For one, entry level boards should stay close to entry level prices. There will always be a ~$50 board, and they should be available by this time next year (6 months after BD launch). Plus, you operate on the fallacy that only highend BD can be purchased. By 6 months post launch, there will be mainstream BD parts as well. PLUS, by next year, the OP should have more euros to put towards a completely new computer. Better to put more $$ in a good build with some room to grow than invest in tech that is already slated for obsolescence. You make it sound like a 3GHz K8 dual core and an 8800 graphics card can't run WOW now, which is absolute bull. No need to upgrade at this time, Doing it now is just money wasted vs doing it next year.