The Taffy Apple
Fish Herder
Oxygen tablets will do..Some LFS's will inflate your bags with oxygen for the longer journey, might be worth an ask.
Could that possibly pose a PH concern? Then again..London to Bristol can be a rather brisk journey late at night..what, 3 hours comfortably? I think it's a great idea with the waterbutt and heater, it will be interesting to see how you get on.
Best of luck lifting all that glass, that is the ONE thing that would really concern me if i ever had to move mine.
Terry.