I'd recommend Maesgwyn Garage, Capel Isaac near Llandeilo. Its off the beaten track out in the sticks.
My son and I both use them for work on our zeds ie. clutch and flywheel, P3 service, springs, dampers,exhaust, laser alignment etc.etc.
Its probably about 25 miles for you, so might be a bit too far, but they do a top job.