You don't want to use a bank's trading facility for this kind of thing unless you are buying and holding for a long time, which I'm guessing you are not doing with the FTSE. For trading shorter time frames you should try something like Alpari or Oanda. These are quite well respected brokers. You don't have to pay commission, you just pay the spread. You could also try spreadbetting (don't be put off by the betting part). It's the same principle you just in £'s per point instead of using 'lots'. It's also exempt from capital gains tax. GKFX is good. If you are paying £12.95 commission (Or whatever it is with Barclays) everytime you trade with a £1000 account, you are going to go broke very quickly! Good luck.
Sam.