Locks that work

Seeing as I'm moving down soon, I'm going to have to kit myself out with some londonsafe© locks.
Already got my little Evo mini D, which I'm sure will do for front wheel duties. Going to get one of those alarmed jobbies and some locking skewers for the LHT but I'm still torn on my "primary" lock.

m18
fagettaboutit
some kind of monstrous chain

I've got a feeling the fagettaboutit will be too small to be practical..?

M18 is the same as a Fah, only longer, but stupidly heavy to the point that I can feel the weight of it on the back of my bike (I carry it on the rack).

Chain are a nice deterrent but they won't last as long as a M18/Fah and the extra weight is a bit off putting, I use mine to lock my and the missus bike against the wall in the flat.

oh and one last deterrant, put a Tesco bag over your saddle when you lock it up - your bike will look shit in second.