Hi tamborine,
I got my wheel clamp from the 'Under a Tenner' column in the local paper - it was �10. You can buy them new in motorist shops but especially at trailer and caravan dealers.
The rotor arm is more likely to be the part. It's located under the distributor cap - if your car has one. That's the round component (black or red) which the ignition leads come out of. It's at the other end of the leads to the spark plugs. It's not a good idea to keep removing that though.
If you want to quickly remove a component overnight and pop it back the next day I would suggest the HT lead. Depending on your model of car that's the single ignition lead that plugs into the middle of the distributor cap (surrounded by the other ends of the spark plug leads). The other end of the HT lead plugs into the coil which is usually a silver cylindrical component.
I think a wheel clamp is the best idea. It's not much fun messing around under the bonnet on a dark and rainy morning or night. Hope that helps.