he's probably right the whole unit might need changing go to a plumbing shop they will tell you what is required. like my kitchen tap can't get washers they only do the whole tap inside bit with washer. seems like days of washers are numbered on newish stuff.
my guess is I will get banned but the clowns who run this forum have been told they should shift baths and showers from DIY to the bathroom appliances section but see fit to leave it where it is anc confuse everyone. And of course you do get ones for example put car questions in motorhomes and caravans some because the tow the car behind the motor home and think its the right place instead of cars section
Bob
October 2012