I think for £50 a complete bike isn't that bad.
It literally needs a morning of my time and £0 spent on it to make it roadworthy?
If it is a total piece of rubbish and I can't get on with it, then I split it or sell it on. Might even switch it to a singlespeed.
Endless possibilities
The Gazelle? Because it's a piece of crap. £50 is a pretty average price for it.
edit: Sorry that came out a little strong, but it's not that good a deal - old, gas pipe steel tubing, not very good components etc etc