just checked out silex website and they look okay but i would be careful using someone they recommend as they could be friends ,an independant witness for court acts on behalf of the court to explain any technical issues and only answers questions put to them rather than giving their opinion on the quality of the stone or the fixing so your questions need to very precise and direct such as "does the 16mm ramp in the floor meet the current uk british standards" ,also make sure that you get witness statement form as many other contractors that may have been party to any conversations that took place regarding the quality of the stone and the fixing it may not look good for the customer the fact you warned him about the quality of the stone and he ignored your advice as this was the time to reject it, hopefully he will have all the correspondence from lapicida assuring him a quality finish ,its terrible when a job goes like this but I have seen this happen far more frequently in the past few years