Closed valley roof

[Alastairreid]

By the time you fork out for a surveyor and any legal costs it would be cheaper getting a proper roofer to re-do the valley properly.
Ask the staff at your local roofing or builders merchants for recommendations.

 

[datarebal]

go to a local roofing merchant, ask if they know a good roofer .. they will

 

[ChrisJP]

To be fair, the rest of the roof looks reasonable - it seems only the valleys are a bodge and need fixing. Still, I'm no expert, so getting in a proper roofer to assess the whole job is a good idea