Guys, I must have missed something there...
So for £300 (no more) what cards should I be looking at?
...Oh that's right, it wasn't me who missed it

,
a quiet gpu that costs no more than £300.
There are
zero custom cooled 670's for £300 or less(not just@OcUK either).
If there were, then there would have been different suggestions from me-price/performance ratio wise.
A stock 670 is surprisingly very quiet too, but is totally let down by such an annoying noise that comes from it that would end up having an accident with a hammer if I had one.
'Since everybody experiences noise differently, and a quiet, high-pitched sound can be harder to tolerate than a loud, low hum, we have provided videos including the noise of every card under full load. The relative loudness of the audio has been preserved, so the videos can be used to compare the cards directly.'
This, the TF cooling is even quiet at 100%
You been smoking too much dave?
Shudder to think of the noise coming out that @1150/1500 @ 1.25v.
http://www.tomshardware.co.uk/radeon-hd-7950-review-benchmark,review-32465-12.html
@Op, play the DCU II first, then play another at the same time, you'll find out what's the quietest easy enough.
The DCU II costs £40 more than the HIS on offer here, but if it's the utmost 'silence' your looking for:
YOUR BASKET
1 x
Arctic Accelero Xtreme 7970/7950 VGA Cooler £49.99
Total : £54.98 (includes shipping : £4.16).
Nothing, touches that cooler(on air) for low noise levels as it connects straight to the gpu header, I know, I've got two of them,
when running in CrossFire, they are quieter in gaming than a single WF(that got DSR'd).
Don't get me wrong though, the WF isn't loud when gaming at all, just mine can't be heard, it actually surprised me tbph, it is a good cooler too.
Both AC and WF@idle can't be heard at all though, even with all my exhausts switched off and just the 920 on silent.
If you don't want to go custom cooling, then DCUII or WF would wing it for me after seeing those vids/personal experience.
For the price, you can't go wrong as with anything up to 50% oc headroom available over stock, is rubbing shoulders with the 670, while costing a lot less.