In reply to Cú Chullain:
The problem with small claims is enforcing the judgement in my experience.
My advice would be to send the garage a letter by recorded delivery. Make the letter well written and grammatically correct. Phone calls are often a waste of time at this point and emails are lite weight, easily ignored and often sent to spam folders, whereas a letter on paper has meaning.
Make the letter firm stating unemotionally what you want and saying that if you do not get it you will small claim it.
Taking small claims action online is very easy, but and this is very important, write down any log in`s and passwords and reference numbers because if you lose them the courts service does not have a system to let you reset.
To reiterate the procedure is easy, it`s the enforcement that can be difficult.