I think I've just melted a piston

My car started misfiring really badly last night - I got a compression test this morning and found there is no compression on no.4 cylinder. There is oil coming out of the oil filler cap and has poured out of the dipstick pipe and the engine is rattling really badly.
I'm going to take the head off on Monday to confirm it, but I'm pretty sure that's what the problem is.
So, has anyone got a spare G engine going? Please e-mail me at
[email protected]
I'm going to go and cry now...