Rain getting in...

[vinn]

Use google for building terms.

You might see blockages of mortar or debris, or water running down the cavity, or sodden cavity insulation or rusted cavity ties, or more modern looking ties? Take photos.

I see no indications of insulation injection holes, & its doubtful that the cav insulation installers would drill and inject from the inside - unless the heavy pointing is covering the holes?
Do you have transferred paperwork for cavity insulation injection from the previous owner?

 

[^woody^]

I won't have a leg to stand on in court will I?

You said that someone had replaced the roof. You claim against them, as it has clearly not been done properly.