Moved onto a TB9 which unusually for TB9's had a constant speed prop, straight after PPL.
Move on to the Arrow II (CSP, Retractable) after about 80 hours total. (PPL completed just under 50, so 30-35 post PPL.)
Why? Convenience really. The TB9 belonged to the school that I trained with, and was generally reserved for PPL's rather than training, so have much better availability.
When that school got taken over, things went downhill quickly, so I changed clubs. The new one had only two aircraft, one of which was the Arrow, so it made sense to get checked out on both.
dp