A friend of mine recently bought a used car from a local dealer and is having problems with the garage.  I just wondered if you could give her any advice regarding her legal position?

As the car was bought in England then could I direct your friend to this information on the Citizens Advice website, there is an algorithm which gets to the nub of the issue and will give the correct advice.

The relevant law is the Consumer Rights Act 2015.

If the garage in question subscribe to the National Concilliation Service ADR scheme then this may be another route that your friend can pursue.