I second the recommendation for the Arcam rHead, at the price you can find it for you won't do any better as a UK based customer.
For headphones it is difficult to make a recommendation as they are such a personal preference. No matter how good sound quality is it means nothing if you can't stand wearing them. And only you can decide what you find comfortable. However I will offer a few to try and consider. The Sennheiser HD 6xx family (600, 650, 660) are very highly regarded and there are bargains to be had. The Sennheiser outlet store has some terrific B stock offers. Polar Audio (UK distributor of Beyerdynamic) often do cracking B stock offers too. I got my T5p's from them for £399, and they were brand new with a 5 year warranty and nothing B-stockish about them. If they are still available at that price them they are a fine product. The Dt1990 model is also worth trying. A truly lovely model is the Oppo PM-2,maybe slightly above your budget but a few weeks ago I picked up a brand new pair (still factory sealed) for £430 and they are staggeringly good IMO. The Akg 712 remains a nice pair of headphones and can be picked up cheaply. A wild card is the Sony MDR Z7, they have just been replaced so you may get a good deal on old stock. I have a pair, they are probably not for everyone as bass is quite pronounced but they are beautifully built and hugely enjoyable I find. An under rated model well worth trying is the Audio Technica MSR 7, very good model that. This is not exhaustive, the best thing is to try as many models as possible and decide which one you like best.