With IB you can trade European stocks including FT100 from a single Universal account. I am not a US citizen so I'm not sure what regulatory restrictions if any apply in US.
I think IB's comissions are probably better than most if not all retail brokers in UK.
In UK CFDs are popular for several reasons. High (insane ?) leverage, ease of shorting and exemption from the 0.5% stamp duty on stock purchase being some of them.