The only problem I have encountered was shading, which was not allowed for by the installers. After 8 years I decided to replace the serial inverter with a multi-channel Solar Edge inverter, which treats each panel separately, and does not reduce the output of all panels to that of the most shaded. The results fully justify the additional expense, and the higher efficiency of the new inverter has made a significant increase in electricity generated, all be it in the sunniest summer since 2010.
In June 2010 I had 18 Schuco solar panels installed on a SSW-facing roof of my split-level bungalow. The best inverter at the time , a Sunny Boy, was installed in my garage. The local firm in Macclesfield sadly went out of business, but the system has worked well since it was installed.
The company that installed the new inverter is Perfect Sense Energy based in Manchester. They provided knowledge and cooperation that resulted in a very efficient installation, and I recommend them without reservation. The contact I had was