The outside of my extension is to be rendered and clad.

It is over a year since the external doors, bifolds and windows were fitted. Gaps around frames had spray foam applied by the fitters and externally this has now yellowed in the sun. Some gaps are small and other gaps are larger as shown in the photos. What is the best way of sealing and preparing these gaps prior to the rendering and cladding being done. I'd like to limit cold spots at the gaps and make it airtight. Is it just a case of more spray foam of some sort, or is there such a thing as insulated render board, or putting some cement or mortar mix in ?

Possibly XPS-insulated tiling board. Seems to have reinforced (?)GRP on each side, made to take internal plaster, which would therefore happily take render. XPS is used outside in below-ground EWI (whether it needs to be or not - discuss - in another thread!) so no problem in this location. Sorted (?). Even better, just checked for vendor - Jackoboard is one, and they do varying thicknesses. Whooppee! Seems made for your job.