As I said I don't have a conection with the company except as a customer.
I have and continue to use a number of avionic companys in the London area including the one that you have had the "problem" with.
They are usualy my first port of call for instalation work, for box fixing I use another company.
I can't coment on the quality of the work on your aircraft as I have not seen it but this company usualy works to a very high standard, unfortunatly unless you lay on your back with your head under the rudder pedals you won't see this, it will usualy give years of trouble free service, something that I can't say of a lot of the avionic instalations that I have seen.
Three out of four of my aircraft have had avionic work from this company and I have had only one small problem (that was fixed very quickly) and I will continue to use them in the knowlage that they will cost a bit more than some but in terms of reliability it will be money well spent.
If you take the time to look at my profile you will see that I spend most of my time "skulking" about in an airliner and would guess that I have seen a few more avionic instalations in the 30 years that I have been in the aircraft engineering business than you have.