steve
this is how we read the rules (but the FSA apparently won an award for plain english a few years ago which had those in the industry, who have to wade through the rule book, coughing into our drinks!)
FSA rules on RETAIL client money DO NOT ALLOW companies to take funds as margin against their positions (strange as this might seem). If you are designated as Professional AND have agreed collateral title transfer on your money then a company may intermingle your funds with theirs. Generally a company will insist on this if you are very large or you take big positions in markets like small cap stocks that require large cash deposits with brokers.
NO we cannot remove funds to cover running losses (as this might impact other clients funds within the segregated fund) . What we can do is offset winning bets against losing bets (but only up to the level of the winning bets). So if clients have £30m deposited but are running £1m profits and £6m losses the company MUST still retain £30m in the segregated accounts.
So the companies MUST have the resources to be able to fund hedging losses even though the clients may not yet have taken them.
WHEN AND ONLY WHEN a loss is realised by the client can the money be taken from the segregated account
This is how Capital Spreads has always read the rules (and we have had several inspections from the FSA on this matter and they seem to agree)
Simon