Thanks John, since they say below rather than before TDC, they seem to be talking about the piston's vertical position in the bore, so the timing would be a long, long way before TDC in crankshaft degrees. That is good in terms of getting maximum power from the engine, but causes a risk of kickback on the starting rope if the person pulling it falters a bit as it approaches TDC.
You said the breaker point cam is "loose" during timing. Is it not fixed in relation to the flywheel itself? If it can move relative to the flywheel, it is not possible to use fixed marks on the flywheel for timing, which means you cannot use a timing light. It is nearly 50 years since I had an early Villiers (it was probably made before WW2) but my uncertain recollection is that the cam was rigidly attached to the flywheel. The flywheel mounted on a taper on the crankshaft, with no keyway. Having no timing light at the time, and no idea what the breaker gap should be, it took hours to set the thing up (I bought it with the flywheel detached from the engine).
