Avoid Myprotein as you say, the quality is garbage and it's cheap for a reason. It gives me and nearly everyone I know who used to use it bad guts. I actually thought I had IBS but as soon as I switched from Myprotein whey, it seems to have cleared up and I'm fine, but still using whey
I currently use CNP as a brand, just because I get it at a very good price. However, GoNutrition or BulkPowders are meant to be very good. I used to use TheProteinWorks but they seem rubbish lately in terms of stuff being in stock and the products having ingredients changed