Genghis - his issue is this simple
He was the lower a/c on approach and the PA28 driver had the onus on him to maintain seperation....which he clearly didnt otherwise Genghis wouldn't be posting this...
Fast / Slow a/c in the circuit can be quite tough...esp if you are the faster a/c in a busy circuit. Wide circuits are fine if you dont infringe noise abatement. Personally where I fly if I think I am getting too close to the slower a/c in front, I just take early flap down wind - at any rate (safe) slow flight is always good practice isnt it? I fly a PA34 which has a circuit speed downwind of about 120mph clean, so the flaps always come down midpoint whatever...dont rely on ATC to seperate you either....I've come unstuck like that before.