Builder Not Finished Job

Reed1

Builder in my village, gave me a quote to do work in bathroom. Wanted money upfront, so did bank transfer, he did alot of work, but still need cabinet, radiator caps, extraction fan put in and finish sealing floor. He has had all money, promised would get rest done. However, when contacted him because its been over month, he says hasn't got time, will refund, send bill. As agreed £300 extra ontop of original quote to get cabinet and put in. Now he's blocked me on messenger, won't respond to emails or calls, so won't give me money back, or finish work. What can I do? I have original quote for entire job, and his signature on it, I know his address, and phone number, what is my next action to get my money?
Thanks 

Reed1

Can anyone advise 

Aylesbury_Duck

Letter before action, small claims court if needed. 

swajarbal

I would contact Citizens Advice (you can online chat to them during working hours) and just clarify which is the best course of action. You may have to give 14 days to allow them to remedy the situation if they have breached the contract, then send a letter before action (and allow another 14 days) then go to small claims court. This is what we were told but our situation was slightly different, in that our job was abandoned part way through and the builder wouldn’t come back to complete.