How long can FSA regulated brokers cancel trades due to wrong price feeds?

[WinFX]

Does anybody know how long back a broker regulated by the FSA [Financial Service Authority) in London can cancel a profitable trade due to a wrong price (in their opinion)?
As far as I know NFA-regulated brokers in the USA only have a few hours. Is there a similar time limit in the UK for regulated brokers?

 

[Pharaoh]

I'm not aware of a specific rule for the FSA. If a broker screwed you by retroactively nullifying a bunch of trades, the best thing to do would be to contact the FSA and FOS and see what they say the rules are.