Just the head, or a whole tripod system?
Really depends on what lenses you'll use as the total weight capacity is a critical factor for tripods.
Anyway, personally I've been most impressed with the Giottos kit I've bought. Seems better built and more stable then the Manfrotto stuff and it's cheaper the the Gitzo stuff (which is eyewateringly expensive).
I'd probably buy the
Giottos MTL9361B aluminium legs (£90) and I would definitely buy the
Giottos MH1301-652 ball head (£70) which is a little over your ideal budget but it's what I want for about the same money.
I was looking at a new ball head for my legs and went down to Park Cameras with my camera so I could actually attach it to some tripod heads and the Giottos series II heads were miles better than any other ball heads for similar money.