[Loz]

Is there a Scottish equivalent to the Small Claims Court? If so, that's you best bet (cheap, too).
After the legalities are sorted, I foresee a nasty injury from slip involving the shower and a bar of soap - most accidents happen at home, you know!

As for damaging his BMW - it's your civic obligation to do so, regardless of anything he's done. BMW drivers ... don't even get me started.