As you can see from my profile, for my sins, I'm in three countries. Which is one PITA of a commute - although it's (sob sob) dropping down to two within a month

I ended up with a US account at HSBC (who actually have considerably more branches then ING's internet banking based ING Direct - which BTW operates similiarly to the ING Direct in the UK - even down to that vile shade of orange(!)) by getting an introduction from my UK bankers (First Direct/ HSBC) - but then again I had oddles of paperwork to prove who I was and who I'd worked for and an SSN by the time the account was opened :-)

I got a US Amex card by talking to those nice people at Amex in Brighton - I've heard mixed stories about how successful that is these days - but if you've got an Amex you might as well ask! Amex Europe to offer an International Dollar Amex card, but please ensure you have smelling salts at hand before you see the charges

As people have mentioned, the main issue is getting hold of an ITIN/ SSN. These days an ITIN is probably what you'll end up with, my wife has one. However try to ensure that you get a real US government issued one - some banks had a tendency to try and issue a number in SSN format but which was only valid on their systems(!!)).

As you can realise, SSN's are both a blessing and a curse! I won't even go into the identify theft issues

Realistically, with all the problems associated with the 'know your customer' requirements that the US banks appear to want to enforce, I'd suggest using a USD account through Citibank in the UK... they will do the (USD) check and debit card stuff for you. N.B. You could try (US) citi directly when you pop into the US - they'll generally help with the paperwork needed to apply for an ITIN - and will send statements overseas (which I've used over the years) - but the first option will almost definitly be easier

I doubt that the UK brokerage account approach will work - when TD Waterhouse operated in the UK, the only real relationship they had with the US and Canadian operations was the name - I suspect the same will be found of other brokerages. Obviously YMMV if you have a cruise ship full of money with a US based outfit such as Morgan Stanley or Merrills

The visa top-up debit cards are quite expensive to operate - there usually are monthly fees and high charges for topping up - search on http://www.cardweb.com for details on them and at http://www.bankrate.com for the rates

Good luck!

Tom

P.S. Just to make you cringe, opening a new account in the UK is considerably more difficult these days than doing the same in the US. For people in the US, imagine the identify points system that's being used by some DMV's (cough NJ cough) raised a few notches!
P.P.S. Whilst most of it won't apply to you, you might like to accidently look through the section on US banking system in the book 'Living and Working in America' by David Hampshire when you're at a bookshop. Highly recommended (especially for anyone either being moved by the job or otherwise - HR departments assume you know a lot more than you do(!))