are you planning on sli in future? if so you'll want to think about a 'bigger' psu, it may handle it bu alays nice to have some 'head room' for overclocking, future upgrades etc.
No plans on SLI... I can't see myself going that route really.
Only thing I'm questioning is whether the Gigabyte GA-Z68XP-UD4 is worth the extra £20 over the Gigabyte Z68XP-UD3P... is it?
Yeah, looking at it the UD4 vs UD3P, and £20 saving is biggest saving for least performance drop.