I wouldn't call that a bargain.
The H70 performs worse than the H50 apples to apples. It just has two very loud, crappy, powerful fans slapped on at stock, whereas the H50 has a single, quiet, weak fan on it at stock. Get an H50 and buy a 2nd, $5 fan, and you got a better heatsink for cheaper.
H70 is just impressive in stock configuration because most closed loops only have a single fan (most heatsinks in general, especially mid-range, only come with 1 fan). So it cools well because closed loops really appreciate a 2nd fan a lot, but in reality it's just a terrible closed loop, and then corsair overcharges you basically for a 2nd fan, like $40+ for a 2nd fan. Then people think it's a great heatsink because tomshardware or some terrible review site shows it vs other coolers on stock configurations, and doesn't factor in that the 2 fans on it are loud and the only reason it cools as well as it does.
You can find the H50 on sale new around $39 (pounds, not sure what happens in britain), and used for $20-35. Obviously britain is different and expensive but I don't see a deal.