No, BTC is not traded in whole coins, but rather in decimal increments of coins. The smallest amount of Bitcoin you can buy is 0.00000001 BTC (a one-hundred-millionth of a Bitcoin), which is less than a one-hundredth of a penny in GBP.
Many people erroneously assume that investing  must cost a fortune because the value of each BTC is in the thousands, but in fact the opposite is true: the network is in fact structured so you can make much smaller transactions than you can with fiat currency.