Twelve quid can buy you a lot these days; the LD130 is a very decent rear lamp that comes with Cateye's excellent twist-to-lock mount. You even get the batteries thrown in.
The LD130 is a pretty standard-spec unit, using 2AAA batteries to power three LEDs. They're not hugely powerful but fine for use about town, and the lower output compared to some of the new high-power LEDs means that the battery life is very good, especially in flashing mode, making it good for fit-and-forget commuting duties.
Side visibility is okay; the LEDs all point forward but there's plenty of lens at the sides. The light is nice and water tight too, it's put up with some pretty awful weather while on test, and even if the rain does get in it's a simple job to strip the light down and dry it out.
The FlexTight™ mount – a plastic jubilee clip – can be tightened by hand, and you can fit it wherever you've room. The square mount on the light allows you to run it horizontally or vertically, and the mount has a good range of angle adjustment too. There's also a clothing/bag mount.
If it's a town light you need then the LD130 should fit the bill pretty well. For commutes on faster roads you'll no doubt want something a bit brighter, and there's plenty of choice around the £20-£25 mark if you do. If you don't want to spend the extra cash, and don't need the extra power, the LD130 is a good buy.