Generating your own energy though photovoltaic cells (solar panels), wind turbines or even micro-hydro generators is really not as difficult or expensive as people seem to think. Prices have come down greatly in recent years and of course once the solar panels or wind turbines are installed, every unit of energy you produce is a unit you are not paying for. You can even start selling any excess energy to back to your supplier.
 
Government grants are hard to come by, purely it seems, due to the huge interest that has been shown since they were announced. The Independent has a very good article discussing the issues surrounding these grants and indicates some costing involved in the installation of generation equipment. Do bear in mind however that the article is a year old so these prices will have dropped further by now.
The Energy Saving Trust details UK wide grants available from the Department for Business, Enterprise and Regulatory Reform (BERR) and the Scottish Community Householder Renewables Initiative (SCHRI) grants available to residents of Scotland only.
 
Npower have a scheme where they will design and install solar panels for you, factor in any subsidies you are entitled to (through Renewable Obligation Certificates or other green energy certificates) and then buy back any surplus energy you generate.
 
Good Energy also have a scheme to buy back surplus energy you generate and also subsidise the energy you produce for your own home.
 
If you're interested in wind power and are of a DIY persuasion look at BWEA's detailed information on types of wind turbine, how to install them, arranging a surplus energy deal with your energy supplier etc. They even have a build your own turbine guide!
 
Remember also that renewable energy generation is not just about generating electricity. You can harness solar power or the heat produced by digestion in compost bins to heat your water directly. Even greenhouses are a classic way of harnessing renewable energy. Look at the Energy Saving Trust's list of renewable energy types to see which may be best suited for generation in your environment.
Also the Centre for Alternative Technology has some fantastic information on all types of renewable energy generation and what will work best for you. The information sheets are packed full of knowledge but, I'll warn you now, get very technical.