New roof fitted, GRP valley advice needed before I pay!

Hi there i have had a new roof installed. Job is finished now but roofer not paid yet. We have 2 valleys coming off the house onto an extension installed by the previous owner. Now the roofer has fitted GRP dry valleys. Look good from the outside but on the inside there is no membrane fitted under the valley or support boards. Now i could live without the support boards as there are noggins to support the valley from eaves to ridge and nobody should really stand on it anyway. But will i ever get problems from having no membrane under the valley?? Eg condensation? There is membrane nailed to the parallel noggins but like i say none underneath the valley so its just exposed plastic in effect in the loft.

Cheers liam