Have a look here:
www.interchangefx.co.uk - I used them to transfer money after reading a few recommendations on here, and have had no trouble. They offer good rates, and don't charge extortionate fees. You can send the sterling amount you want transferred into their sterling account (by BACS transfer, or that same-day transfer whose name I forget right now!), and they will then wire the money to your account (or your wife's, or any account you tell them to) from their dollar account - it's very quick because they send the money by wire transfer, so it can be in your US account on the same day Interchange receives it into their account.

I arranged for them to transfer some more money over for me earlier this week - they gave me $1.995 to the £ - I think in theory they charge a £10 fee if you're exchanging less than a certain amount (I think £10,000), but they've always waived it for me!
Hope that helps.