If Bitcoin is money and not just something to speculate on why would you want to transfer £'s to bitcoin at a 33% premium when the goods you are buying are linked to the price of £'s or $'s so your 33% down from the offset
The site which the screenshot came from is not representative of the UK market as a whole. The prices you see there are only a very small number of individual sell offers. In at least some cases, the folks behind the offers on that particular site became involved with Bitcoin only relatively recently and thus had significantly higher entry points than the current 'real' exchange rate. The available offer prices were
much closer to spot when BTC was at 75-80 pounds.
UK buyers looking for far better rates can bypass individual person-to-person sell offers entirely and use speedybitcoin.co.uk or one of the other services which charge a small flat percentage over Mt Gox.