I came at it from a different angle, looking for a running jacket for winter that was warm enough - assuming there'll be snow again this year!
Anyhoo, two birds with one stone and all that, I found a bright lightweight jacket - the Ronhill Vizion Microlight - over at Sweatshop's website for £37, down from £60. So it depends what you want to spend really, but I like looking for bargains. (Same jacket is £40 on Amazon, via a third party SportsShoes Unlimited.) P&P for both 4 or 5 quid.
Or you can pick up a Time To Run hi-viz bib vest for £6 on Amazon!