Dan, it is well worth taking a long hard look at your overall energy consumption - 2 people in a 3 bed house should be able to reduce consumtpion to at least half what you are paying.
The obvious and cheap solutions first - replace all light bulbs with energy efficient bulbs, at least 200mm of loft insulation. Then look at heating system - do you have a programmer that allows you to set different times for each day? could you upgrade to a zonal system? Also can you reduce the times the water heater/central heating is on? What type of heating system do you have - a modern condenser/combi could halve your water heating costs (you only heat what you consume - British Gas had a special offer recently - an upgrade for £1400 - about the same as your energy bill for 1 quarter.
Look at your energy consumption habits - how often you use oven, how hot your wash is set, and how often it is used, do you use a tumble dryer? Dishwashers are also expensive - it is cheaper to buy an extra set of crockery/cutlery and only use it every other day! The reality of energy companies is that at any one time one may be cheaper than another - but it never lasts long! However your energy company will test your metering for free to check it is working /recording correctly.
Finally you could consider the costly and intrusive stuff like wall insulation, door and window replacement, self generation system installation - the list is long and can be quite expensive (I was present whilst a salesman quoted a customer £14,000 to install solar panels to a 3 bed cottage!
I appreciate that you may have already gone down this route, but something appears to be very wrong with your energy costs.