I was worried about the 3+ weeks mentioned in there terms to, but in practice they get your BTC out fairly quickly (Normally with in hours, sometimes longer outside of office hours, I get the feeling that someone has to manually release the coins rather than it been an automatic process). So they aren't perfect, but if you want to convert GBP to BTC they are better than most of the alternatives.
Having already put cash into 'finex, my mind is more on going the other way - using a UK-based exchange to withdraw via (Finex => BTC => Netagio => bank).
Any experience with the speed of their GBP withdrawals?
To be honest, I've never tried to withdraw GBP from them, so that could be where the 3 weeks comes in. It might be worth checking out Dalmars brokerage account for the withdrawal.