No tax i would risk it, the fine is only back dated to when you last paid tax on it, i wouldnt drive with no mot or tax though, can you not go get it mot'd now ? Take an hour off work and just turn up at an mot station.

I begrudge taxing all my cars though, i only drive one at a time and when i am not driving them they ore off the public road on my private property. I'd pay extra to have transferable tax so i could list all my cars on it and sway it around depending on which car i was driving.