I've had a spat of punctures lately and my mending-fu seems to have deserted me lately so I've just bought 10xContinental Race28 from High On Bikes on eBay for £21.95 delivered. Should see me through the week. Not necessarilly the cheapest to be had (Ribble were knocking them out 50 for £80, £1.60ea) but it will do. Still remarkably cheaper than Halfords.