I think you are mixing up bells and pedal reflectors. Riding a bike without pedal reflectors when its dark is illegal.
RVLR 1989 Schedule 20
Requirements relating to obligatory pedal retro reflectors and optional pedal retro reflectors to the extent specified in part ii
1. Number: Two reflectors on each pedal
2. Position–
(a) Longitudinal:On the leading edge and the trailing edge of each pedal
(b) Lateral:No requirement
© Vertical:No requirement
3. Angles of visibility: Such that the reflector on the leading edge of each pedal is plainly visible to the front and the reflector on the trailing edge of each pedal is plainly visible to the rear
4. Markings: A British Standard mark
5. Size of reflecting area: No requirement
6. Colour: Amber