If you are classified as a pro trader you would pay income tax and not CGT on trading profits. Likewise spread bets would not be tax free. It would depend on other sources of income (eg if you had a full time non trading related full time job) and also frequency of trades.
If it is deemed that you would pay income tax then look at possibly setting up a limited company. An accountnat could tell you if this was financially sensible or not. Up to £300k the tax rate is approx 20% compared with income tax of say 40% from 40k onwards. Above 300k then it is more like 30%. If you wanted to pay yourself out of the company profits you would do this via a dividend and the tax rate depends on amount taken etc.
There are obviously more complications than this but hope it helps.