Remember the guy will still need his ESTA. It is $14 direct on the US Homeland & Security site and a simple process assuming he is a good boy. Lasts for 2 years (my only problem is remembering when they expire, I renew mine once a year just in case - 10 mins online).
I'd be interested in hearing people's experiences of the US Embassy in London. When we were in Belfast visiting the PEO several taxi drivers remarked that a lot of people fly over just to visit the US Consulate in Belfast for their visas as getting an appointment in London is a nightmare (or something like that).
