I feel your pain. Try a new set of plugs, rotor button and use some "Start ya bastard" or some other similar product. Before doing so remove the fuel pump fuse and turn the engine over for 30 seconds or so to clear any unburned fuel. If it does not work at least you have a spare set of plugs that you can rotate.
If it does not start check the plugs for wetness - this will at least tell you whether your injectors are working.
Also - a stray thought, have you checked to see that your distributor is firmly clamped. If that has rotated it could be a timing issue.

__________________
Alastair from South Australia
1971 280 SE 3.5
1981 300D
1980 300D