The damaged side tells only part of the story
Observing a wet ceiling from below may show where water arrives. Testing fittings and supplies above can help establish how it got there. Without that access, the engineer may be unable to test the relevant possibilities.
Arrange permission before attendance
Speak to the occupier, landlord or managing agent as appropriate. Agree entry to the necessary spaces and identify who controls communal isolation. A key to your own flat does not authorise work elsewhere.
Avoid deciding liability from a stain
The investigation reports plumbing evidence. It does not settle which party is legally liable, what a lease requires or what an insurer will reimburse. Keep those decisions separate from the task of establishing the source.
Related service
Flat-to-flat leak detection explains the practical investigation and the scope to discuss before booking.
For agreed residential work, the Exact Source package is £1,400, including applicable tax. Necessary access, plumbing repair, materials, suitable checks and a Trace & Access report are included. Decorative and remedial reinstatement is excluded.