Quite a few to choose from really ranging from £75 to just over the £100 mark. Lots of the 500-700 lumen ones around and so just keep your eyes open for one on a deal. I have a Lezyne Super Drive that I got for £40ish on some sale from wiggle about 6 months ago and just picked up a Niterider Lumina 700 off of ebay for £52.50 for my dad for xmas. The latter is a great little light with a cracking pattern.
If it's only going on the handlebars then without doubt get an Electron Terra 3 which can be had for around the £50 mark and it don't get much better than that for 800lumens and a 3 hour burn time. Only issue with the Terra is that it doesn't appear to be quick release ie. it doesn't slide off it's mount. It looks permanently attached.
Other lights would be Cateye's nano shot plus and light and motion's urban500. Usually one is on an offer and they are all pretty good performers these days. Moon xpower500 and Cygolite have a similar 500ish lumen unit as well.