Well I've spoken to the company and it looks like I'll get my money back, but basically they think the problem is the chip having been tampered with and so basically it's unfixable - everything worked on their testing equipment so I guess they must think it can only be that.
Although, bear with me on this... I looked at quite a few Terrano's before I bought this one, and several had had the dash replaced. I think they all had false mileage as in they had started from 0 again when the new dash was installed. From what the repair guy said, when they replace the chip they download the info from the old chip to the new one so that the dash still displays correct mileage. So is it that this Terrano fault causes the actual chip software to fail and it needs to be wiped in order to work, thus losing correct mileage? I could be way off here, I know nothing about any of this, just something I'm wondering in my basic logical way...
Anyone know of any of these going 2nd hand?