Skidding: difference between track and road frame

48/16
I guess I should be spinning more? Thing is, with a larger rear cog I did not get a very high speed on flat and downhil was a nightmare.

Well you have a choice, either keep your gear and be unable to skid, or lower it, learn how to spin to get the same momentum, and then have the best of both worlds.

I'd recommend 48/18, or even 19. You'll prefer it in the long run.