Water leak(stains) on the ground floor utility ceiling

Hi, We see water leak(stains) on the ground floor utility ceiling which is right below the shower cubical in the 1st floor. Insurance team experts come to our house today said the leak is because of grout deterioration and seal not being there in the shower cubical. Looks like my insurance company won’t cover this damage/loss I can see the flooring below to the one side of shower(next to try) is very damp and I can see water when I lift the vinyl flooring. And wall adjustment to the shower where our study is also damp on the below. I need advice on my next course of action.. Can I ask for one more visit from the expert to confirm if the leak from grout deterioration and seal ? Is there one company or person I can get all the things done? What will be the approximate cost for this in UK ? Thanks