ICE, look into GWS for your powerplants. You can build a mini shocky out of 3mm depron and power it with a GWS IPS-A motor. I know you are in the UK, however check out this site, http://www.balsapr.com/ to compare prices of GWS stuff.
Another good source of info are the discussion groups at www.ezonemag.com.

You can always build a trailer to tow behind your Mini. or do you guys call them caravans?

Whack