If somebody does work for someone else, provides a service, or supplies goods, and does so as a business to a consumer, then under the Consumer Rights Act 2015 the:
Goods must be as described
Of satisfactory quality
Fit for purpose
And any service must be as described and carried out with reasonable care and skill.
If no price is specified then the price must be “reasonable” and if no timescale is specified the timescale must be “reasonable”
If on the other hand goods are being sold by a private individual to a private individual, they only have to be as described.
In the case of a vehicle it also must be roadworthy otherwise it’s a breach of section 75 of the Road Traffic act.
In your case, it is apparent that these guys have failed to carry out the job with reasonable care and skill or to do so within a reasonable period of time.
You now need to specify a timescale to get this sorted. I wouldn’t worry about the resin factory burning down, he can get that somewhere else.
The first thing you need to do is get a quotation for putting everything right.
Armed with that you can tell him that unless this is all sorted complete, done, dusted and finished into a satisfactory standard, by the end of this month, you will issue Small Claims Court proceedings without further notice.
It needs to be in writing.
The new Moneyclaim beta system is easy to use: https://www.gov.uk/make-money-claim
the new system is much better than the old government Gateway system.
You can prepare the proceedings now, at your leisure, save them, and then just pay the fee and press the button when the deadline in your letter before action, expires.
It's then just a case of following the court process and responding to any emails that you receive.
Thank you for letting me assist you with your legal question. I am glad that I was able to help.
I am not certain whether that answers the question for you or not, but I am happy to answer any specific points arising from this.
It will be my pleasure to help you again either further with this or any future questions you have