Why its worth building a cheap scabber up or even better a scrappy bike 10 - 15 quid your lock will prolly be worth more.
I tried this, but even running to the shops some bits didn't work right, some needed replacing etc and it wasn't fun to ride into town. So I swapped a part or 2, cleaned it up, and now I like it, while it's still under £50 the time and effort means I still would be gutted if it got stolen.
I just don't leave any bike anywhere out of sight.
Fear of theft ranks up there with the weather and the traffic to put people off cycling in this country.