You're a wiser man than I am
I always forget to add tubes to my PX orders and my LBS sells them for £10ea - hence mending is the only option!
I've been putting the job off for so long - I rode the falling leaves sportive back in the autumn with no spare tubes in my pocket
You are a better man than I am.
I stock up on 99p Planet X inner tubes and chuck the punctured ones straight in the bin....