The government has recently announced Green Homes Grant. It seems to offer a voucher scheme for up to two thirds of the cost of hiring tradespeople to upgrade the energy performance of their home (up to a maximum contribution of £5000). Low income households will be eligible for up to 100% funding, up to around £10,000.
Information on this new grant and other grants that may be available can be found here:
www.simpleenergyadvice.org.uk