There are no maximums and minimums under SOGA. you either comply or you dont. So provided the dealer complies, the customer actually has nothing to complain about. The problem is that many dealers either do not know what they are actually liable for or deliberately try to evade their liabilities.
Whilst pursuing SOGA can be distressing, but it is the correct way, and perhaps dealers will begin to take their responsibilities more seriously if customer were more savay about their rights.
There is an important difference between warranty under SOGA and manufacturer and extended guarantees, and in the absence of the manufacturer, a purchased insurance based guarantee policy may be sensible choice. But it will depend on the details.
It is also worth pointing out that some manufactures use insurance based guarantees from new, so even though the manufacturer may have gone, the insurance company underwriting the guarantee may still be out there. The premium will of course have been paid so the policy should still be in force. The problem is identifying which manufactures use this scheme, and then convincing the insurance company that the caravan owner is the beneficiary.
I do not know if Avondale were party to this type of scheme.