Thanks for linking my pictures CliffordK and thanks everyone for the advice. I think I'll start by trying the fiddly method of tightening the front bolt with my fingers and if it doesn't hold I'll find a cheap Allen 5mm that I can hack. I just really need to get that one off my bike because it's very uncomfortable. Also I don't necessarily want to change my saddle because I'm comfortable on the one I have and I don't know the first thing about finding a saddle that suits me.