Going back to Mary Whittington's original question, there is nothing to stop you plugging a storage heater into your mains system and consuming some of the solar electricity which would otherwise go unmetered into the local network. No electricity companies are installing export meters; they are guessing that 50% of the solar electricity will be used by you and 50% exported, and paying you for 50% (in addition to the Feed in Tariff). I suspect that most of us will be exporting 90% of what we generate because of the mismatch between generting it when it is summer daylight and consuming it when it is winter darkness.
In winter you can set up a storage or fan heater to run when there is spare generation. It is very crude and fiddly, even with 1 kW and 2 kW output settings. Everytime a cloud goes past you would need to switch the heater off. To automate this you would need an export meter, a control box, and a thyristor block to limit the heater input to match the free power available. There is nothing on the market at the moment and the sukaelectroheating.co.uk equipment is not suitable. I expect someone out there will be inventing such a system in their garage before too long, but it is a minority market and unlikely to be on general offer. In any case, you might be able to shave £20 off your gas bill each winter doing this (£20 off economy 7 bill too). Hence it's not really worth investing in, especially if electricity companies might fit export meters in the future, which would make it all poinless.