My garage is quite some distance from the house, so no chance of extending the central heating. It is, however, very well insulated.
I bought a cheap 2Kw fan heater as a stop-gap until I thought of a better solution, but last winter I found that even on the coldest days it was perfectly ok to work in there after about 40 minutes - and that's a space 10m x 7m x2.5m. Very often I ran it only on the 1Kw setting, and turned it of after an hour or so, so I don't think i'll bother with anything fancier.
The central heating option could be a very good one, the only disadvantage I can think of is that your garage will be being heated even when you're not in there, so it might work out a bit more costly than it needs to. I guess it depends on how much time you see yourself spending in there.
