Looks like what I really need to do is fill in a form:
CAA Form 123 (SRG1759) Issue 00 Standard Change/Standard Repair (SC/SR) embodiment record
The form will need to be signed of by your engineer...
Release to service
This SC is not suitable for release to service by the Pilot-owner.
..however they can only install the antenna by...
Additionally, the following applies:
— The antenna is installed in non-pressurised secondary structure areas, unless the location is set for this purpose in the airframe documentation or provided by the TC holder (i.e. NTO), or the antenna is being exchanged and has the same footprint.
— The antenna is located in a distance to other antennas appropriate for the aircraft and the antennas.
— The antenna is compatible with the connected equipment and is suitable for the environmental conditions to be expected during normal operation.
— For aircraft certified to operate in known icing conditions, the new antenna is located at the same position and has a size similar to that of the existing antenna being replaced.
— Instructions and tests defined by the equipment manufacturer have to be followed.
— The performance of the new antenna installation or of the new antenna type has to be confirmed during testing after installation (e.g. range of radio).
4. Limitations
Any limitations defined by the equipment manufacturer apply.
So the bits in bold would require a written procedure from the PilotAware team, for the engineer to follow. I suspect the post installation tests would need to be defined too.
The $64,000 question is would you engineer perform the install and sign it off if the information was provided. I'd suggest you give them a call and discuss it.