The 12kgs are firm without being harsh. No need to slow down for speed bumps....... well anymore than usual.
My spring numbers are :-
Front 10kg 62.200.010
Rear 8kg 62.97.255.008
Rear 12kg 62.97.260.012
The BC spring part numbers are the spring specs. Your fronts have an internal diameter of 62mm top and bottom with an uncompressed length of 200mm and a rate of 10kgs. Your rears have an internal top diameter of 62mm, internal bottom diameter of 97mm, free length 255mm and spring rate 8kgs. So you've got the same springs as I do.