All interesting comments. I'd say that most SB cos will be delighted to take £1000pp bets, so long as you consistently lose. If there's any chance you know what you're doing (which I assume is the case), life will soon become very difficult! They'd soon spot what was going on if you tried splitting positions across accounts, too.
Interesting view. Why would they want to annoy somebody that gives them £2000 (FTSE example) in spread for every trade they place. I think you will find trading that size you will get a dedicated trader ,putting your orders straight in the market, and get all the schmoozing that a high roller should expect.
If it's in the market then I would bet money on them doing it for you.
JK