Confidence: It might be this.
Notes: Nymph. Looks a good match on UK Hemiptera website (see http://www.britishbugs.org.uk/heteroptera/Miridae/deraeocoris_ruber.html). Black-and-plum body colour, dark base to pale legs with a dark spur running into the paler lower legs. Hairy beast and decidedly shy: always retreating around the stem of the plant it was on when I tried to get closer. Hope it will be feasting on our blackfly!