Hi,
You've got 2 options really
Air source heat pumps - Less expensive than Ground, but still costly as hell, starting at about £10K. May be worth it in the long run tho and will add to your "green" points, more info below..
http://www.worcester-bosch.co.uk/homeowner/products/air-source-heat-pumps
http://www.ecoheatpumps.co.uk/
Wet heating system - you know what this is about, the company who invented it and also the economy 10 tariff (in conjunction with Scottish Hydro) have their website here...
http://www.electric-heatingcompany.co.uk/
If you go for the wet system, Eco 10 is the best tariff for that system by a mile. It either wont work, or ruin you, if you try any other tariff with it. If you go for Air source, it'll depend on the application you chose, however Eco 10 may still be your best bet.
You may need to confirm the supply you have to your property can support the expected loads of these tariffs. Once you know what your going for and how much load you'll need, contact your distributor directly to confirm this. (if you do need an upgrade, budget at least 2k for this initially)