A friend & I set to build mine years ago when my speedo in my 85 Mayfair broke. We designed it on paper first, brainstormed for several evenings over several beers (try it - it's amazing what you can come up with!), then started collecting parts. I will need to dig out a pic (don't have one to hand at the moment as I sold the car 8 1/2 years ago), but amongst the parts used were:
A top rail sliced up.
Lots of MDF & Vinyl
Coin tray from a Montego
Manual swtich for cooling fan
"Push Once" button from a bus (used as the starter button)
Speaker for the CB constructed from a broken oil pressure gauge and a clock radio.
Remote control for the Sony Radio.
Centre speedo repositioned in front of the driver
4x 52mm dials surrounding the main speedo
52mm Tim tacho in pod on the top of the dash
CB Radio
Cubby hole from a Transit
Pin switch for glovebox light from a Volvo 440
Glovebox light from a Vauxhall Astra
Some plug chain
A Mini badge.
Lots of glue and ingenuity, granted, but well worth it. Plus it is different to anyone else's. It was even featured in Mini Magazine's report on Mini in the Park in 1999 (October edition, page 68 under title "Dashing Off" if you're interested) 