On the offchance this is a genuine query (which if it is well done everyone else with your 'owl' jokes) I'll answer.
Your local GUM clinic is here:-
Tel:-01904 725401
Monkgate Health Centre 31-33 Monkgate, York, North Yorkshire, YO31 7WA
They won't inform your parents, and you will be able to get all the applicable tests free of charge.
Far be it for me to critisise or judge you, just be careful how you go at parties- things can get seriously out of hand sometimes and you don't want to end up with no meaningful life ahead of you. Practice safe sex and have a think about how much you really want to be behaving like this when at 15 you can't have seen much of life yet. There are other things to be doing as well so don't screw it up for yourself.