Thank you for the further comments, in general things have got worse unfortunately to the point where me and the owner have pretty much had a communication breakdown.
The price has remained the same but they have agreed to put right any damage so we will see. I am unsure on the certificates and at the moment I am just hoping they complete the works to an acceptable standard as any further probing by me directly with them I think is going to cause big problems. As far as I am aware all is waterproof, they did put external marine ply down on the floor and stated that they filled and waterproofed all the floor before putting the levelling compound down. Unfortunately taking photos has proved a bit difficult as we haven't always had that opportunity.
I probably had the most worrying phone call I have ever had with the owner when he stated they would arrive at 10:30 then texted to say 11:30 then by 13:30 hadn't turned up. I sent him a polite but firm text explaining that I wasn't happy and that this wasn't the first time we had issues with their timekeeping and he effectively tore into me stating that he runs a successful business and I have to work around him, any times he gives are not guaranteed and I will need to accept that, I'm too controlling, I should give them a key to the property and not look at the bathroom until it is complete then I wouldn't moan so much, if he has an emergency he will prioritise that over us and I have to accept that, etc. In essence it was like he was doing me a favour not taking £000's of pounds off me for work I have paid for.
I tried to explain my side but he wasn't happy and stated that the work would be completed on the agreed date and whatever times they wanted to work they would and as long as they completed the work I should accept it and stop complaining. I tried to explain that I was simply making him clear that when I pay for a service and get given a time of arrival I expect that time to be adhered to (within reason) and if not to be notified. He felt that I was dictating when he had to be at my property even though it was him giving me the times!
To be honest the whole ordeal has made me feel really ill and I am really surprised that someone who is accredited on so many levels can treat me, my family, and my home in such a disparaging manner. I have spoken to Which as he is a trusted trader and they have confirmed that they feel the treatment is unacceptable and have recommended I allow them to complete the works, make sure it is to an acceptable standard, and then consider a complaint. Funnily enough on the checkatrade website one of the guarantees the traders have to sign up for is 'Keep appointments and arrive on time (calling in advance if they need to reschedule)' so maybe he has forgotten that!
They have also left a heap of rubbish outside the property for about a week now and every time we remind them to remove it they just say they will tomorrow and never do.