What do you mean by 'all cables'? 'all in the ceiling' or 'all in the electrical installation' ?
For either, it depends on what was found, and if there are any further comments about the state of cables in the rest of the installation that need to be addressed.
In terms of 'have to', in terms of rental properties there is a period of time to address C1, C2 and FI codes in legislation.
In workplaces, the dutyholder has duties under Electricity at Work Regulations to make sure the installation is safe.
In any installation, the insurer might also have something to say if serious problems are not corrected, and a claim is subsequently made.
Yes, you may have to install them. You do not have to remove and replace every PVC clip, but ensure that there are non-combustible ones (usually metal) at appropriate distances.
