They have now been back and agreed that the flooring needs to be replaced. Tiles are on order and they will book a slot to carry out the repair work.
Thanks for all the replies as I think it began to make a difference when I was able to more clearly (and firmly!) articulate the issue from a more informed perspective - a great forum!
Thanks for all the replies as I think it began to make a difference when I was able to more clearly (and firmly!) articulate the issue from a more informed perspective - a great forum!