Hi Anthony,
Well done! Another Magnette back on the road.
You don't mention whether you have kept the standard engine/carb set-up, but it won't affect my reply much. Obviously, if you have changed the engine or carbs, the standard timing is unlikely to be very relevant, so you need to check the recommended timing for the model that the engine came from.
These days we have another problem to deal with too: modern petrol. It doesn't behave much like the stuff that was being pumped in the fifties. It has greater anti-knock properties, so in general will tolerate more advance than the old stuff. This being the case, setting the timing for optimum performance is a bit more experimental than it used to be. I generally add 5deg advance to the standard setting and then do a road test, focusing on situations where pinking would occur if it is advanced too high (e.g. pulling from low speed in top gear or going uphill in top). If it gets through this test without pinking, advance it a bit more, re-test and repeat the procedure until pinking occurs. Then wind it back to the last pink-free setting.
If you have a timing light, it is a good idea to check what happens at various engine speeds. Static timing only sets the timing at one point, without the engine running, so it is really only a start-point to get the engine running before you tune it properly.There is a good article on this on the Tech website:
www.zmagnettetech.info/maintenance/ignition/79-ignition-timing
You will probably also find the distributor article useful too.
Good luck!
Malcolm