Power Generating Companies

Powergen: got half the fossil-fuel power stations on privatisation
Innogy: Formerly National Power, got the other half.
Cogen: Subsidiary of Innogy specialising in CHP
British Energy: a merger of Nuclear Electric, which owns the nuclear power stations in England and Wales, and Scottish Nuclear which owns the Scottish ones. Now branching into traditional power generation also.
BNFL: British Nuclear Fuels Limited. Runs a few older nuclear power stations, and one hydro plant. Web site verges on the unusable, with Shockwave and buggy Javascript.
Eastern Group: a distribution company for Eastern England, which leased a few power stations from PowerGen and built a few of its own. Now a subsidiary of TXU Europe, along with Norweb Energi. Their site now contains no information on generation, perhaps they've got out of it?
First Hydro: runs a couple of pumped-storage hydro-electric plants in Wales. A subsidiary of Edison Mission Energy. This is a very nice site.
Scottish Power: Regional electricity company for Scotland. Run Coal, Gas, Hydro and Wind power stations in Britain and Ireland
Humber Power Limited: Owned partly by British Energy and partly by Elf Aquitaine
Slough Heat & Power: Subsidiary of Slough Trading Estate, provides heat & power to the Trading Estate.

As always, if you can improve this list, contact me