Hi Graham, sticky situation! I'm also surprised you can't get a new or used crankshaft (if that's what you mean by 'the big end'?) in Thailand.
Have you posted on:
Thailand Motor Forum - Thailand Forum
Maybe someone there can point you in the right direction…
It's 1000 kms from Ranong to KL - can't you get a (tow)truck to take you to the border? I can't understand why no thai truck driver would be willing to do that… Forget couriers…
Another idea: Find a good toyota mechanic in thailand, perhaps through the above quoted website, or talk to the thai toyota distribrutor to find one, get the car there to determine the exact problem (sounds like you're at the wrong garage if you 'think' the problem is the big end, i would want more certainty).
Once you know what part you need, order it from KL, or order it from any number of parts dealers in Australia, a lot cheaper, and faster, then getting it shipped from the UK.
See for instance:
TOYROLLA SPARES - Quality Used Toyota Parts, Used Car Parts, Used Auto Parts, Wreckers
Toyota parts Toyota wreckers & used Toyota car parts locator
J T W Auto Parts : Home
or do a google for toyota parts australia
good luck, and let me know when your website is working, perhaps now with all this time up you sleeve you can look at it :-)
also, do drop us a line when you get down to melbourne - we're planning a similar trip, in opp direction, w. 2 kids…