The biggest breaker bar you can get your hands on, in 1/2" drive. At least 1m is preferable.
Rubber mallet, for the times you need to give something vaguely breakable a clout.
I know you've mentioned spanners, but decent ratchet spanners are a must have (Halfords Pro range are excellent).
A 'Big Bertha': A long, thick shafted flat blade screwdriver. Often used more as a lever than as an actual screwdriver.