Only leaks in driving rain
This often points towards an exposed junction, flashing, verge, ridge detail or defect that admits water from a particular direction.
A leak is a symptom, not a diagnosis. The most useful first step is to work out when the water appears and which roof details lie above or nearby.

This often points towards an exposed junction, flashing, verge, ridge detail or defect that admits water from a particular direction.
Do not assume the chimney masonry itself is responsible. Flashing, pointing, pots, flaunching and the adjacent roof covering can all contribute.
A small defect can take time to saturate surrounding materials before staining becomes visible indoors.
Check outlets, edges, upstands, joints, splits and areas where water remains standing.
Water can track along timbers or underlay, so the indoor mark may be some distance from the external defect.
A single obvious defect may be repairable, but the surrounding covering and the reason it moved should still be checked.
Ask the roofer to explain what they believe has failed and how the proposed work addresses that failure. For anything more than a very small repair, a written description of the work can help avoid misunderstandings.
Where hidden damage is possible, ask what happens if further defects are found once the covering is opened. Photographs before and after the work can also be useful.
Use the MyJobQuote service to describe the job and look for roofers covering Blackpool.