FranArch

Detail 2 but use Yellow as full filled cavity insulation (mineral). Otherwise you will have a massive thermal bridge. This is a standard detail. The doors should be moved left on the brick and the frame should overlap the cavity insulation at least 20mm for building regs.

It depends on the type of cladding: A) Treated Timber (Larch) B) Acetylated Timber C) Thermopine There is a huge difference in durabiity and costs. If you want to have max durability increasing a bit the cost (+60 years) option B is your best friend.

I had Admiral when I was freelance, was around £370 py and you can do it online without asking to brokers.