Looks like you lose 4 points on exchange rate though (GBP > EUR > USD as far as I understand the Unicredit website correctly- unicredit is the bank covering the transfers for bitstamp). And having a USD account in the UK probably also doesn't make sense because SEPA as far as I understand is only for EUR denominated transfers..

//edit: that said, if you create a EUR account in the UK and use transferwise to convert your GBP into EUR you avoid the 2 bid/offers but only pay one. So you end up with about 2 points + whatever transferwise is away from mid-market. Cheaper than the above but still relatively expensive.