If you are unhappy with the quality of the service you have received and the original fault was not repaired, you may have the right to have the work carried out correctly or a price reduction, although the garage will need to present you with a final bill. The test for this is that the work was carried out 'without reasonable skill and care', but the garage may be reluctant to accept this version of events. You have the option to get a second opinion from another garage or vehicle engineer but you should agree beforehand with the garage how the cost of this will be divided and that both parties will accept the outcome. You can also refuse to settle the bill if you are unhappy, but they can hold on to your vehicle until you pay. You can also settle the bill and write 'paying under protest' on the invoice and receipts so that you can continue to pursue the matter afterwards.