Hi, I've jsut seen your message...
for going short you could look at some of the companies that provide spread betting. I have an account with IG Index but there are other companies out there too. See
http://www.e-traderuk.co.uk/spread.html for a list of providers. Some people like to have multiple accounts so that can choose the best price/spread.
Be very, very careful about spread betting. there is more to it than just selling before you buy. A good read is Market Speculating by Andrew Burke. But since most spread betters lose money you should practise on paper before you do it for real and understand the complexities involved compared to trading shares.
At the moment, there is increasing interest in going short as we approach the 3rd leg of the bear market. This correlates with the last leg of the bull market when it was posisble to make money by throwing a dart at a board full of tech shares.
Be wary of this - it is true that going short can return profits in a market that is descending but as the market goes down the risks increas and it is still possible for the market to up by 30% in a short time.
Good luck and DYOR.
There are people out there who are losing there houses due to insufficient research.
PS. Can't comment on T20 as I don't know of a stock broker that provides the service. T3 seems to be the norm now but the in principle buying on a delayed payment can only be good if your judgement is proved correct. You might even be able to sell before the payment is due and make a profilt. Another idea is trading on margin. Again spread betting companies provide this service if you wish but you are leveraging your capital and it is vital that you understand the both the advantages and the disadvantages of this and know about stop losses and targets.