Sentinel has it right. Unless you are willing to keep this thing going until it goes too far then your best bet might be to just not be where they are waiting for you to show.
It sounds like a silly territorial thing that wont go away with pepper spray. Sure that would be goddamn satisfying to spray some goof after the crap you and your mates take but it would likely be short lived.
I am in Canada and I only speak through my own experiences and what I have read of the situation with youth gangs in UK. You live there and have said yourself that the likely event would be retalliation from them as a large group. You would need to answer with more of the same. Where would it end?
Be the bigger man, realise that life is full of assholes ,and no matter what you will never get rid of them. You can choose to battle them all in vain or to coexist. Its not runnin off or being a nancy or wimp...its more like acknowledging and respecting the fact that a mans body doesnt always have what it takes to act out what is in the heart and mind.
You're mad, insulted, intimidated, frustrated etc. and the old testosterone is kickin in telling you to attack. My advice, only do so if you can do it with no weapons. Its more mature ( read :'manly') to avoid a fight you know you will lose than it is to go out looking to put a hurt on someone with a weapon.
Am I making any sense to ya? Just MHO. Take care and good luck solving this one.
Peace