This may be on a tangent but you don't need a Form 1 with a radio, for it to be installable on a G-reg.
An FAA 8103-3 is just fine, if the radio is a new part.
In fact, from digging around a while ago in CAA docs, any paperwork providing
traceability is good enough, but nobody has a financial incentive to tell you that
What you need to do an installation in an ICAO CofA aircraft is Approved Data (e.g. a TSO), which is a different thing from traceability.
Would you like to explain all that to the CAA, LAA and BMAA, who unanimously seem to have a different opinion. Yes an FAA 8130-3 is fine, but the XCOM doesn't have that either, (according to Michael Coates, owner of XCOM when I spoke to him recently) in spite of being assembled by NARCO now.
The fact that personally I would make more profit selling and installing an XCOM instead of a Funkwerk radio to a Jabiru/Sport Cruiser/whatever is certainly not a financial disincentive.