I think he was just wearing that moustache as a disguise as he was helping alan/joanna get away from the police. it is fake that's why it suddenly appears in that scene.
I thought it was because Alan and Joanna were dressed as Nazis - Alan was dressed like Hitler with the little tash so i assumed that's why Boycie had one too. Maybe I'm wrong, i dunno, that's just how i took it.
Maybe the moustache signifies that Boyce is going to become the next Statham, he is in all his classes and is going out with Kim who works in the same office as Joanna. Maybe things are going in a circle!
I don't know its an impossible choice, i'll just have to hope that when I flip the coin it somehow explodes and kills me.
And Sue was singing the circle of life so maybe things do go round in circles in GW.
............................................. every time we touch we get closer to heaven, and with every sunrise our sins are forgiven, you on my skin - this must be the end, the only way you could love me is to hurt me again and again, and again....
i think it was both his way of showing Statham appreciation and as a disguise, at least it's better than dressing up in nurses uniform like Statham....oh wait....Boycie already did that!