Having reached a decision I thought I would post this so as to help others. My decision wont be everyone's cup of tea but I feel satisfied with the route that we have chosen. Obviously, time will tell.
The results of the shading analysis came through from company B but it didn't show issues with shading under the dormer. The amount of shading beyond the chimney on our house was significant but no where near as bad as I had expected. That said, it was obvious to me that shading was going to be an issue with panels in portrait mode under the lower dormers.
Shading above the dormers both from our chimney and from the chimney and aerials of the house next door was certainly evident but not especially significant.
Company B offered us a range of solutions between 2.5 and 3.5KWp using two different brands of panel and micro converters on each solution. Having taken up communication with a couple of the references offered by company B I was able to monitor the real time statistics of their systems using the web portal. One of these had shading that was worse than ours and only in the afternoon. The other had pretty minimal shading for the whole day.I invested (or, as my wife felt, wasted) a huge amount of time looking at their real time data and it was quite amazing how the panel outputs varied during the day: not so much the whole array (or strings of) but panel by panel. All came to the same total harvest over the day, but each was going up and down quite significantly and not in phase. Admittedly, I haven't been to the properties but, with minimal shading confirmed by each during certain times of the day, I put the variability down to clouds and reflections.
Now, in my case, we have some shading to contend with. We also have potential lack of space under the dormer. Panel placing in landscape mode may address some of the issues but it does compromise the theoretical maximum panel coverage. Company B suggested that we place all of the panels high up above the dormers where the shading would be least and that any shading issues we have could be addressed by micro inverting. The KWp would be a function of panel choice and the obvious suspects such as HIT Sanyo panels would provide the biggest theoretical harvest. I still have some reservations about micro inverters being a new and unproven technology. We were offered the standard 20 year warranty that Enecsys offer together with a 10 year insurance backed warranty so as to give us 10 years peace of mind even if the installer decided to explore "different avenues". As part of the negotiation I got the installer to agree to place the inverters in the roof space. That way, if one of them went south the repair would be much easier than being outside.
The end price was pretty competitive at the end of the day. My feeling is that it has to be a win for both supplier and customer. This, I feel, sets the relationship on a good footing and should maintain a sense of good will going forward.
I know that the MI route isn't for everyone. I hope though, with 14 Sanyo panels we will get a good harvest and be very satisfied.
This forum has been an invaluable source of information for me. I'm so pleased that I found it. Thanks to all for your help.
