Just so you know, if you fly with American Airlines to/from London, you can use your old passport in your maiden name if you want. The key thing is to take your original marriage certificate (or an official copy) and hand it over along with your ticket and passport at every inspection point.
I had to buy a new passport a couple of months before I left for the States in 2005 so now I have one in my maiden name that is valid until 2015 ... I changed my name on my AA mileage account soon after getting married, but I'm a cheapskate so I decided to try to hang on to my new old passport for as long as possible.
I've booked and flown on American three times since marrying - each time using a ticket booked in my married name. At DFW, Gatwick and Heathrow airports, the initial pre-check-in security processing took a couple of minutes longer than normal while the security staff checked the green card, the ticket and the passport against the marriage certificate to confirm both my names were there and I was me ... and added a note into the computer system. (I've been a useful training exercise a couple of times while junior checkers were shown what to do with me and my paperwork!) After that, the actual check in itself has been totally normal because all the details were already in the system.
I flew to London and back with AA this January, again using my married name with no problems, even though the US has changed its passport/ID rules.
Obviously I can't comment on what all the other airlines do ... And your experience and mileage may of course vary ...
However, as long as the US or UK don't change the rules again, and while AA sticks with its common sense approach to this issue (and I stick with them for the airmiles) ... I've got no intention of forking out such a ludicrous amount of money for no good reason.
There endeth the essay!