As part of my planning permission research I had ascertained that Building Regulations would not be required for the works "provided the installer is registered under Part P of the approved document", which they were.
But as part of the overall system installation cost, Firegrass also included a structural survey to ensure that there were no issues associated with the increased load on the roof, etc.
As my property was relatively new and certainly in pretty good condition I had assumed that this would be just a cursory inspection.
However the structural engineer spent quite a bit of time carefully looking at all aspects of the roof construction and, much to my surprise, he did find a number of issues. These were all associated with the original construction, where some aspects of the way the individual roof trusses were cross-connected for rigidity, was not done to the required codes.
Fortunately it wasn't anything very serious, and the rectification was something I could easily do myself, and I wasn't required to do the work before the installation was carried out - but I have to say I am actually quite pleased that such a thorough job was done!