There is no single answer that fits every church, but infrared radiant heating is the strongest all-round choice for most parish churches. It heats people and surfaces directly rather than trying to fill a large, draughty space with warm air. That means fast warm-up, low running costs and no damage to historic fabric from circulating hot air drying out woodwork and plaster.
Underfloor heating suits churches with stone or tile floors that are being relaid anyway, but the installation is disruptive and it works slowly. Fan-assisted convectors can top up a radiant system in very cold weather, though on their own they struggle with high ceilings and poor insulation. Heat pumps are gaining ground in well-insulated church halls but are rarely practical in a Grade I listed nave.
Start with what you actually need: how many people, how often, which zones. A small midweek congregation of thirty in the chancel is a different problem from a packed nave on Christmas morning. The right system solves both without heating the whole building to the same temperature all the time.