Hi Jon and welcome. Thank you for your kind words re the forum.
As an AirBus driver I can't go into specifics about the 1.4 engine, other than check it like you would any normal watercooled engine. Look for clean oil, no white emulsification on the oil filler cap, check the exhaust isn't blowing, does it start well, does it idle consistently, are there any running problems? Is the expansion tank up to the correct level. You get the picture.
With everything else it's simply a case of having a good look around. Check the following points:
1. Is there any evidence of corrosion on the lower 6 inches of the Bay? If so - why?
2. Has the Bay been undersealed and Waxoyled?
3. If a poptop is fitted - does it all work correctly ie is the canvas clean and undamaged, are lockdown catches in place, has the roof been marked by the poptop rubbing against the body of the roof (if it hasn't - it's a rarity!)
4. Check the gutters for corrosion - not just what you can see standing next to the Bay, but what's over and inside the gutters.
5. Is there play in the steering - a loose wandering steering wheel that constantly needs correction is the sign of a steering box problem. A gentle amount of correction is normal.
6. Do all the gears engage properly? The Brazilian gearbox is notchy not sloppy - gearlever travel is long but not loose.
7. Ask if the gearstick has ever snapped - if so how long ago and where did the replacement gearstick come from.
8. Do all the electrics work - check them.
9. If an on-board accessory heater such as a Webasto or Eberspacher is fitted - check that it works.
10. If there is a gas hob and fridge - check that they work.
11. What does the Bay ride like - it should be firm but not harsh - lowered suspension causes a harder ride. A particularly hard ride up front could indicate a lack of grease in the front suspension/poor maintenance.
12. Does the Bay have documented service history/bills to be seen? The more, the better.
I'm sure there's more but that should kick the list off. Have fun searching - it's a great time to buy.
Tim