Unfortunately this idea is almost entirely technically/chart based as I don't believe I can make any legitimate fundamental calls on the direction of the FTSE/UK economy until at least after Tuesday and Wednesday's calendered Bank of England events. Even then I believe it is likely that I will be waiting until after 7th May 2015 (UK general election) for the Bank of England to to do anything substantial as obviously a change in political policy will have an impact on the they implement. Anyway on to the idea...
The weekly chart of the FTSE 100 has recently made a lower low followed by a lower high which by definition is the start of a downtrend. Couple this with the fact that price has broken below the of 6300 where accumulation was clearly being made in October 2013 and October 2014 I am lead to think that there are no more buy orders here and so supply for the time being has overwhelmed demand. The next obvious levels of demand/where there maybe buy orders to stop the decent of price at least in my eyes are 6100 and 5900.
In all likelihood I'd be looking to profit from this decent by shorting components of the FTSE 100/250 that are already falling. However if I had to place a trade on the FTSE100 I would be looking to the and hoping to enter short on a rally to 6300 with entry (and supply!) there being confirmed by some sort of candle pattern, with a stop loss around 6450 (hopefully tighter if price action allows) and my profit targets at the levels of demand mentioned above, 6100 and 5900 respectively.