Not familiar with the MG6 engine but I did have an MG2.
Dipping a modern plug with an unglazed porcelain tip in petrol will not do it any good, old plugs had the tip glazed. If you suspect fuel is not getting through to cylinder put a drop of petrol down the plug hole, replace the plug and see if it fires when you crank it over. It could be the timing is out, does the MG6 magneto have an impulse unit, this flicks the magneto over faster when hand cranking to give a better spark, if it has you should hear it click when you turn the mag over.
I am sure one of our club MG6 experts will be able to give further advice. Good luck with the project.