Best method of insulation is to insulate the wall externally.
No issues of interstitial condensation as the whole wall structure beneath the insulation is kept warm,so no cold briging either.
The drawback is that it is expensive compared to cavity wall when used in a retro fit situation,but is worth considering if your walls are in poor condition or you other were going to render your house anyway.
Many modern buildings do away with the cavity altogther and use aircrete with external insulation.
Wih this method and the right specification of insulation,it is possible to have a house so well insulated that,little or no heating is required,what is known as a passive house.
Ground source heat pumps and solar energy can be used to genrate what little heat is required.