Relax, Jaymz. People are trying to help you and you're snapping at them.
The Spyderco UK pen knife was designed specifically to fall within the UK's restrictive legal guidelines. They are slipjoints, and as such, do not lock. DO NOT LOCK. They are legal for you to have and carry, even in Glasgow.
Other good choices would be traditional slipjoints, such as those made by Case, Queen, GEC etc. There are a host of knives by these makers and others that you can legally carry. Though it sounds like you are looking for a weapon. Slipjoints make for poor weapons. A nice, stout umbrella or walking stick might come in handy if you're concerned about yobs.
Good luck to you, sir.