I've just started work and I've met a lot of incredible people. The problem is a guy I get on with so wll " As A Mate!" asked me if I would go with him to a leaving party for someone from work! I don't mind going with him as a mate but I think he wants something more, the biggest problem is he is 10 years older than me!! What am I gong to do?

The first question you need to ask yourself is this, do you possibly have romantic feelings for him as well? The reason I say this, is that generally when people in your situation are afraid to tell someone they only want friendship, it is often because they are worried that there's a part themselves that may want more than that down the line and if they do, telling the other person they don't might blow any future chances for a relationship!
If you are certain you only like this guy as a friend, then you should do the right thing by him and let him know where he stands! There's nothing worse then leading someone down the garden path and giving them false hope, yet many people do it out of weakness and carelessness. Keep it real and tell him that you value his friendship but that's all you want to have with him.

I agree with LeanneDucan. Even though he might want more, he needs to know how you feel as soon as possible so that he doesn't get the idea that you're leading him on.