Well it seems I would have struggled to get the wrong
glow plug length as mine had extensions on the short ones to make them
long - hence my earlier question about thread length.
Changed them today. It took about 2.5 hours and I have no previous experience working on car engines. Most of the time was spent debating whether I could put something back together again if I took it apart. Re-assembly only took about 45 mins, despite wasting at least 20 mins of that trying to retrieve a socket that wouldn't free from the tightened nut of the foremost plug.
Hopefully these pics might help someone who like me was debating whether they were capable of this job (no pics on the fact sheet and some of the steps listed were unnecessary).
First the end product, after reassembly (hopefully the same as the initial state except with new
plugs)!
First step was to go for a run in the Bongo to warm up the engine. Apparently this reduces the chances of a plug shearing when removing them. You don't need to remove the gearstick links as stated in the factsheet (at least not on the manual gear shift). You do however need to remove all the fuel line gubbins as in the pic below. Two bolts several hoses and about 5 electrical sockets need undone (note where they all go back). Perhaps this is unnecessary if you do remove the top panel and gear links, but access looked very tight if it is possible.
Remove the bus bar and the old
plugs.
Fit the new
plugs. I used a fine coating of copper grease on the threads to ease future removal. Reassembly is simply the reverse of the previous steps.
After this hopefully the Bongo will start and run more smoothly from cold. Mine seems to be smoother, but I guess I'll find out for sure in the morning.
I'd hope next time it would only take me an hour or so, but I'll be fitting the relay mod to hopefully prolong the life of these
plugs.
Hope this is helpful to someone.