Electric bike from spare motors

Hi Everyone, my first post here. 

I've been thinking of making an electric bike. Now there are bikes on the market that are $450+ and I have a spare one that I haven't touched in over 6 years lying around. With the recent improvements in DC electric motors, I think it's about time I gave it a shot at assembling an electric bike.

The motor will likely come from an electric lawn mower, the battery will be a lithium ion battery rated for that motor (I can attach these into series or parallel depending on what motor I use). I've been looking at electric motors from Kogan.com.au (I'm australian) 
Either one of these http://www.kogan.com/au/buy/18v-lithium-ion-cordless-garden-tool-set-3-piece-set/
or http://www.kogan.com/au/buy/recharge-mower-electric-lawn-mower
The cheaper one more likely. If I should source a motor another way then I'm all ears. 

My questions are: Would the motors in the first link be powerful enough (they use the same battery as an electric drill)
How would I attach the motor to the bike so that I can ride and engage the engine when I want? How would I mount it so that I can use regenerative braking? I was thinking of using a clutch sort of mechanism attached to the wheel axle, again I'm all ears.

And if anyone's done this already, what type of hazards am I going to face? (that probably aren't obvious, safety first!)
I also thought of using a petrol engine from a lawn mower but an electric bike seems more appealing to me. :)

Thanks all