Same card, that's cheap. I've never bought from maplins before though(except stuff like LED's and solder). The warranty is probably just shorter, as it's an inno3d card and EVGA have better warranties. The scan free delivery is available if you link your scan account with the bit-tech forum, instructions are in the scan subforum.
460 is a great card. i've got a pre-production model which has lower stock clocks than the one's you get now, but mine overclocked on stock voltage to 800/1600/4000 easily, while still keping the fan quiet enough and the temps below 70. runs bf3 on high@1080p. bargain!
Brand new either the GTX460 1GB or the HD6850 are the best buys. The GTX550TI is totally pointless unless it can picked up noticably cheaper (like £25+ cheaper). Second hand should get you a HD5870 or GTX470 at a squeeze but TBH I would just get the GTX460 and clock it. I used to run both a single GTX460 and 2xGTX460 in SLI. They rocked. One of the ones I had clocked to 925/1850/4300 which made it faster than a GTX560TI in pretty much everything. If you are interested in GTX460OC performance then check out any review that includes the GTX560 (non Ti). It is identical to the GTX460 but clocked at 810/1620/3800 out of the box (up from 675/1350/3600 that the GTX460 came clocked at).