Greeting from the midlands , Martin!
Funny you should mention heating, My Joiner mate and I where discussing just the very same thing the other day, as it stands , we are going to sort out the screeding and flooring of the workshop, then kingspan the exterior wall , ( garage is attached to the house) then once thats done, we are going to board and Insult the roof, aswell as the exterior wall.
That with the draught less Door should massively aid the thermal effeciency of the workshop, and I reckon with the extractor system and machine running heating will not be an issue.
BUT, if it is , then wooley jumpers and a small log burner are being considered, especially as we will be able to burn some of the resulting chips from the machine.

Alluminium sure does burn pretty lol.

Rik.