In this tax guide, it states: "Under Section 532 any currency other than the euro is an asset for the purposes of capital gains tax. Accordingly, a chargeable gain/allowable loss can arise to a person buying and selling foreign currency otherwise than in the course of trade. That gain/loss is computed by reference to the corresponding euro value of the purchase price and the sale proceeds."
Worth considering spreadbetting FOREX, it is treated as gambling so there is no tax on gains/winnings.
Most people lose money trading FOREX though, unless you’re going to commit to it full time and learn the necessary skills I’d suggest it is best avoided.