Long story but will try to be brief.
We had planned and got an estimate for a completely new shower room to replace the existing one and got a fitting team in place.
In September 2018, went into a local Kitchen/Bathroom studio as Mrs Hogweed had seen a vanity unit, sink and taps at a very good price. Whilst there the proprietor was charming, and offered all sorts of discounts if we bought other items. His displays looked good, prices seemed ok, so we ordered everything except the tiles. All was promptly delivered to the shop but he said he couldn't store it for us so we had to take it and store it at home. No problem , we have a spare bedroom.
Due to unforseen circumstances (illness) the fitting team weren't available until well after Christmas, but they eventually came and started in March 2019.
On day one they hit the first snag as the shower tray drain sat directly over a main joist. This obviously wasn't seen until the bath and floorboards were ripped out. Our fitter had his team there and needed to proceed, so he rang the shop to ask for an exchange and was told to put it on a leg set. He also said the proprietor spoke to him like he didn't know what he was doing! We didn't want this, so I OK'd him to get another tray, identical in size but with an offset drain and the job proceeded without further hitch.
We later went into the shop to ask for a refund, even offering to take a partial one for the traders trouble. he said he'd see what he could do, saying he'd speak to the rep of the supply company.
We heard nothing for a couple of weeks so I rang. The proprietor said the rep had said no to a refund, so I asked him for one as he was the trader.
He refused saying it had been custom made (no it wasn't, I looked at the company web site)(LIE),
then it hadn't been stored correctly, (why wouldn't we?)(LIE), next he said it was damaged (how would he know, it was at our house and it is STILL in its original packaging)(LIE).
He then bluntly said he didn't want it back and we should keep it as a spare! IT'S A 1.7m X .7m SHOWER TRAY. THAT DIDN'T FIT IN THE FIRST PLACE!!

He then told me to put it on E Bay saying we'd easily get our money back.
It's currently on at half what we paid for it (£250) with no interest.
I tried to get a refund through my credit card but they knocked it back.
So, apart from that we had a lovely new shower room.
Now to part two (sorry but it gets worse).
After just four months my wife noticed the vanity unit had split, not one but THREE of the panels, so I took the door off and we went to the shop. His face dropped when we walked in but I produced the door. He said that shouldn't have happened and asked if it had got wet!
"It's a bathroom unit, what do you think? Condensation, and maybe the odd splash when the grandkids are staying and cleaning their teeth, but other than that, no".
He said he'd look into it, and e mailed his supplier (and copied us in) stating the unit had failed during normal usage and should be replaced free of charge under guarantee. It was rejected, the contact saying it had got wet (again we were copied in). He then claimed any further claim should be made directly to the manufacturers as it was no longer his responsibility as we had admitted the unit had got EXCESS water on it, (the word excess was never mentioned) (LIE). And yes, we have copies.
But, he did tell us the unit was no longer available (LIE, I googled it, it's readily available on Amazon) but he (happened) to have one in stock that we could have at a discount price as a favour to 'valued customers'. His discount price is higher than the cost on Amazon
Meanwhile,
We contacted citizens advice who told us he was responsible under the Consumer Rights Act 2015, so we made him aware of this. We also followed the Citizens advice on protocol, asking for his official complaints procedure and if not an alternative dispute resolution scheme.
He has responded with a letter yet again claiming he has taken legal advice (doubtful) and he is no longer responsible as the unit wasn't fitted following the installation and the aftercare guidelines weren't followed(LIE). He also claimed in the same letter that his secretary had witnessed my wife admitting our grandchildren had splashed the unit. (LIE). It was me that had said they may have occasionally splashed it. when cleaning their teeth.
We are now at letter before claim stage.
What I want to know is should I go for a full refund (both shower tray and unit, total £380), just the faulty unit, (£130), extras such as fitting a new unit, and time trouble and stress chasing this up.
(About 7 years ago I filed in small claims court on behalf of my daughter who's landlord had refused to reimburse her £100 bond. At the time the owed amount plus three times that amount could be claimed, £400, I know this as that's what I claimed, and he backed down and paid the amount claimed + three times it + my court fee. Is this still the same?).
Sorry about the length of post, all advice greatly appreciated.
PS a mate of mine also had a similar run in with this company about 15 years ago, presumably the now owner/proprietors father.