Does anyone know what Western Union would charge to transfer $6,000 from the U.S. to the U.K.?

You will have to call them up and find out. Via the web, there seems to be a $2000 limit. From California the cost for 2 grand is $114.

Check out Citybank's c2it (http://www.c2it.com) service. They charge a flat fee of $10 per international transfer, but you can only transfer $2000 per 4-day period. I believe the limit may be some sort of legislative requirement.

You should contact your bank and ask about EFT (electronic funds transfers). I don't think there are any limits (we transfered over $50k at a time). It costs about $80. Much cheaper then WU. It has to be from bank to bank and it helps a lot if you use large national branches versus small/local/co-op