I had something similar, needing some work done (a downstairs loo before my no longer mobile mother visited from abroad). When I finally found someone, I paid them way more than they asked as a deposit, to demonstrate how grateful i was that they promised to get it done.
Chased them for ages, always excuses and no work done at all, til i found small claims
Its very straightforward and importantly includes the option to charge interest on the money, which is then applied from the date it was owed, which i took to be the date the work should have been done. This gives you some pressure to apply to the person who owes you, the longer they take to pay, the more they will owe you.
The pressure was enough for me to get my money back in full. I filled up the form, so i understood how it would work, but before submitting it, just saved it ready the go. I then send a letter by registered post so that i knew it had been received explaining that i was ready to make the claim if i didn't receive the money back by noon on . Doing the form meant that knew I really was ready to do it. The interest meant that submitting the form would increase the amount owed.
I send an email copy if the letter too, after it was delivered and received, got an email back by return, followed by all the money back in three instalments. I needed to reiterate the threat of court to get the final instalment but nevertheless, all of it back. I had realised it had been stupid of me to pay it in the first place and to consider just writing it off, but decided it was a matter of principle.
Court process worked well for me, to apply pressure and get my money back. Good luck.