*** GOV.uk UPDATE ***
According to gov.uk face coverings will be mandatory on Driving Lessons (unless you are exempt) from 4am 30th November.
https://www.gov.uk/government/publications/face-coverings-when-to-wear-one-and-how-to-make-your-own/face-coverings-when-to-wear-one-and-how-to-make-your-own