By definition, sexual harrassment in a legal context may be considered any sexual advance or action which makes the recipient feel uncomfortable. It is not the action that is important it is the feeling it generates. So I would say that this is stalking simply because you feel that it is. Especially if you have told him no on several occasions and he persists like this. Find out where your nearest local police station is and either ring their number (not 999, their local office number) or pop in to talk to someone. Tell them the story, tell them how it makes you feel, ask them what actions you and they can legally take. It may be that the police can do nothing but at least your concerns will be recorded and they may do something like ensure there is an officer somewhere nearby at the times when he does this so they can catch him at it (ok, maybe not with the current public services budget but hey, we live in hope...)