Tradesmen not honoring guarantee

Wellyboots6

My parents had some rendering done on their house by tradesmen they found on the internet, but have since had problems with the render.
The company were members of the federation of small businesses but are no longer, my parents think they may have been kicked out.
They contacted the company regarding the problems and they didn't respond. Eventually the business owner came out and said it needed re-doing, and gave them an approx time to do it, but now they are getting no response again.
Parents have contacted 2 solicitors outlining the problem but have had no response yet.
Any ideas what their rights are?

mo786uk

supply of goods and services act 1982

if work was poor can sue but will need to go to court

gurantees are often not worth the paper they are written on if you cannot get the tardesman back -as you have found out.