Interesting with all the options for Voltage on the ballast. You run with 240V still in UK?
Most of our gear in Sweden uses 10uf capacitor for 125W MV. 8uf was in my Swedish Thorn Precincts though, because they must run at 80W MV only. We never have Thorn's gear here, so it might work differently. We have mostly Helvar ballasts here (made in Finland), very good ones!