(Home) 2Y engine misfiring

Townace - G Reg - 2Y - 1800 Petrol. Had for 3 years and just been for 3rd MOT. Failed on emmision (there is a slight misfire). Just changed plugs. All old plugs look ok - light brown deposits - no oil. Changed air filter. Misfire still there. Slow idle is at about 1100 - bit high? I think it could be timing or dizzy cap.
How do you adjust timing?
How can you (easily) remove dizzy (ie. can it be done without removing drivers floorpan)?

PS. The Townie is my wifes - I drive it whenever I am allowed - it's been good - very useful vehicle - only probs were first mot (no white front side lights - fixed by drilling into headlamp housing and installing 5W lampholders) and blown cyl head gasket causing by the proverbible water leak - fixed for £180 and promise to mechanic to not bring it back!

- (#2896) Paul, 11 May 02