you should post some pictures of your bike.
Broadly speaking, you have:
- three types of motors: direct drive, geared hub and crank drive.
Leave the direct drives alone, they are high power and heavy, not suitable for road legal use in the UK.
Geared hub and crank drive motors are very similar, they have internal clutch and gearbox so that the motor's torque can be multiplied by the gearbox and the drag when pedaling without power eliminated.
- two types of pedal sensors: torque sensor and cadence sensor.
The torque sensor measures your pedaling effort and multiplies it by the assist level. The cadence sensor is much simpler, it simply works out if you pedal or not and to a degree, how fast you pedal.
Torque sensor simplifies the electronic control and thus the wiring. You don't have to fit brake sensors like you would with the cadence sensor because everyone will instinctively reduce their pedaling when slowing down or braking.
Budget: around £500-£700.
Take a look at some of my kits:
torque sensor, hub motor:
http://wooshbikes.co.uk/?tskit
torque sensor, CD motor:
http://wooshbikes.co.uk/?cdkit#tsdz2
cadence sensor, hub motor:
http://wooshbikes.co.uk/?hubkits
cadence sensor, CD motor:
http://wooshbikes.co.uk/?cdkit