Have people noticed Dapol's new signals? http://www.dapol.co.uk/index.php?option=com_virtuemart&page=shop.browse&category_id=114&Itemid=59&vmcchk=1&Itemid=59 - fully assembled, motorised and lit - drill a hole, drop it in, do up the nut and wire it up - off you go.
£25 might look a lot, but it wouldn't be too cheap to do all that yourself..