Front and back i know there are lots out there but any good opinions

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Presume you mean a commuting set.

These are good:
http://www.wiggle.co.uk/p/cycle/7/Cateye_HL-EL130_and_TL-LD130_Light_Set/5360045566/

The mrs picked up a set from tesco that are really bright and even cheaper
http://direct.tesco.com/q/R.202-3716.aspx

Thanks nick the cat eye ones look the ones

IMHO £20 isn't really enough for two decent units. A Cateye rear such as LD600/LD610 will get you seen in most conditions (you do want to be noticed, right?) though the little LD130 / LD150 models are useable. All run on 2xAAA.

On the front the tiny Cateye EL135 (2xAA) is the minimum I'd settle for. The larger models, the EL320 and up, have a bright spot but poor spread. Fenix LD20 (2xAA) is waaay better, waterproof and a truly worthwhile investment. Yes it blows your budget to pieces but unlike the others you are unlikely to feel the need to upgrade after a few trips home from the pub.