I'm pretty sure the price you got the GTX470 for was during the same EOL pricing period with the 500 series arrived and there were some last EOL deals to be had such as the GTX480 at £199.99.
The problem is with the GTX470 was at launch it was same price as the HD5870, but slower and MUCH hotter and high power consumption. Overclocking the GTX470 did yield quite a lot of performance increase (around 20%), but it still put it at around same level as overclocked HD5870 level, but at the cost of even higher power consumption and temp (which the stock reference cooler cannot really cope with). If I recall correctly AIB customer cooler wasn't really that mainstream back then (with the exception of MSI with their Twin FrozR custom cooler and Zotac), so with the introduction of the Fermi cards it also led to the rise for the market of 3rd party graphic cooler for those that wanted to overclock and lower temp:
https://www.tomshardware.com/reviews/accelero-xtreme-plus-v6000-vf3000,2784-4.html
The performance of the cards back in that gen was like GTX460 1GB <10% HD5850 = GTX 470 (stock) <10% HD5870 <10% GTX480 = GTX470/HD5870 (max overclocked) < 8~12% GTX480 (max overclocked). Still remember Nvidia's infamous Crysis 2 tessellated water underground across the whole map that's out of sight to make their cards looks perform much better than ATI's offering at the cost of hurting gaming performance Nvidia users as well (as they also get lower frame rate because of the pointless over-tessellation for things that were not even visible
).