When I first joined this forum, I had never used a base except Pat Chapmans. I was amazed at the number of bases on here and thought a start would be The Saffron base. This I made with Spanish Onions, and the taste of the base in the final curry was to sweet for me, not what I was looking for. The next time I made the base, I used English cooking onions from Sainsbury. The taste was nearer to what I was trying to achieve.
Having said that, some on here prefer a sweeter curry.