Q621: Can you repair vehicles on the road?

Generally, yes you can. However, you cannot repair vehicles on a road if,

it is during the course of a business
it is for gain or reward
it causes annoyance to people in the vicinity

The only exception is that if the repairs are carried out following an accident or break down where it was necessary to do the repairs on the spot or within 72 hours.

If it is a one off repair then this is not likely to breach the law but anyone who repeatedly repairs vehicles on the road is likely to commit an offence.