Roger that...
I've just been scouring the interwebs but not much joy! The ones I had in mind have either just become unavailable or have had a VERY recent price hike
I was going to suggest a Boardman Comp Road bike (all be it for £60 over budget) but they have sold out of the 2010 ones now
The '11 is a lower groupset and is more expensive. The other one thought of was the
Verenti Kilmeston but they have put the price up from £500 to £900 sometime in the past week!
I'll keep thinking and doubtless others will be along soonish to advise...
p.s. is there any flexibility in the budget? Looks like a fair bit of choice at 600 compared to a monkey.