Heated grips are essential if you're going to ride through the Scottish winter (and spring & autumn, often) I fitted a pair when I bought the bike 5 years ago but they've given up the ghost so replacement was urgently needed. To be fair the old grips were £10 used from Ebay so they did ok.
Today I bought a set of "Dr Bike" heated grips from J&S Accessories, 272-4 Great Western Road, Glasgow. They seem to have risen from the ashes of Hein Gericke and have a large range of bike clothing & accessories.
The set consists of a pair of grips, a controller and the associated wiring. Fitting was easy. The kit has a tube of superglue to secure the grips. The left side was tight enough itself and I used fibre glass resin on the throttle grip. Superglue sets almost instantly but the resin gives you a few minutes to get the grip into the right position.