One thing you need to bear in mind if your going to certify ga stuff is your going to need a group rating for your b2. They only way you can get this is through an oral exam after submitting experience sheets. There are no type courses for your Cessnas and pipers etc. This was the case last time I enquired. Contact the new ga unit at the CAA and see if it's still the case. If they can't help try your luck with engineer licensing.
As for LAA and BMAA aircraft there is no real call for radio annuals. If they have an avonics defect then they either fix it themselves or find a b2 at their local ga maintenance facility.
Camo is a separate approval from 145. The camo in the case above would be responsible for issuing the work pack and auditing the company or engineers performing the work. The case above would be an aircraft that is maintained outside the controlled environment.