Share dealing / stock brokering account

Has anyone had any success opening a share dealing (stocks, funds) account here? I've tried opening an account at a couple different firms, only to be told that they don't allow US nationals (something about US tax treaties?). I still have various investment accounts in the US, but I'm a rather passive investor and gambling on the additional variable of currency exchange rate sort of sends my head into a tizzy (especially since the £ seems a bit weak, currently). For that matter, the share dealing options here seem... pretty awful, in comparison. Does anyone here trade in the UK?

One possible reason could be the pending legislation now in committee in Congress, the strengthened 'Qualified Intermediary' initiative (google HR3933 or S1934). Currently, existing accounts with American owners are (for the present) not affected, but some financial institutions with accounts located outside the US are reluctant to open new accounts. If the bills are passed they will place draconian compliance measures on those institutions. It's only concerned with a 'United States person' as defined for tax purposes.

http://www.telegraph.co.uk/finance/newsbysector/banksandfinance/5374095/British-banks-revolt-against-Obama-tax-plan.html

Again, this could only be one possibility. It may be something entirely different.

I've run into the same problem. I'd be curious to know how Americans in the UK invest. Surely there has to be a way?

I was able to sign up with Selftrade.

I only invest in individual stocks with them, and a small amount of money.

Just be careful about US tax reporting and FBAR.