Hi
There are immense difficulties in trying to get this sort of issue resolved. Whilst the Sale of Goods Acts (SoGA) theoretically apply to all retail sales including second hand items, the fact a product is in a second or more ownership complicates matters considerably.
Liability for such issues when proven always follow the contract of sale arrangements, and with caravans it is almost always the case that you have your purchase contract with a dealer not the manufacturer.
The manufacture only get involved if you make a claim against the manufacturer's guarantee, which is a contractual arrangement, but it is governed by the T'Cs of the guarantee. This would only apply to you provided you and the manufacturer agreed to transfer the remaining guarantee when you purchased the caravan. If you did not complete the transfer documentation then the manufacturer has no liability whatsoever to you.
Even if you did complete the transfer of the remaining Manufacturer's guarantee, the guarantee does not cover the value of the caravan, only those points specified in the T&C's
Your only redress would be through SoGA, and you have to bear in mind that whilst SOGA is a powerful piece of consumer legislation, its purpose is to provide a fair resolution when its tenets are breached. So you need to bear in mind some important points.
You tell us the caravan is at least four yers old, It is well into its expected life expectancy, and SoGA recognises that products don't last for ever.
Remedys through SoGA are only expected to return the customer to the conditions if the product had not be come defective. So you should not expect to gain from a remedy.
The conditions a caravan might experience are quite variesd and can be quite harsh, consequently the extent or value of repaires to older caravans may be quite limited.
You tell us "this is a known fault with the Bailey". Just because a fault arrises does not necessarily mean it is a design failure (as per SoGA). As a generalised point, if a product has a design fault, then a substantive number of examples would demonstrate the same fault, and in this case whilst some may have shown it not all have, so a claim of design failure is unlikely to succeed. Consider how likely is it that such a 'design fault' could have gone four or more years before revealing itself?
It's more likely materials or workmanship failure would be the case. but proving in your given circumstances, I suspect would be nigh on impossible.
For a start As Dusty has pointed out, you would need to find a competent independent expert who would not only be prepared to give a signed written report clearly stating the faults were inherent in the design or were present at the time of purchase, but also one who is prepared to stand up in court to swear to the accuracy and methodology of their report and findings. I suspect that your "local dealer " would not be prepared to provide such damning evidence in writing.
Another big problem you will have is the fact the caravan is second hand. Whilst you may be able show evidence to convince a judge you have not any opportunity to abuse the caravan, you cannot have the same confidence about previous owner care and attention. They may well have taken the caravan to extreemes of conditions that might have predisposd the caravan to the damage you report.
What dealers tell you must be accurate. but they are not obliged to volunteer any information, becasue in English Law the buyer must be aware or " Caveat Emptor". As a potential buyer it is your responsibility to ask all relevant questions and to acertain that the product you are thinking of buying is fit for your purposes. Do you have any evidence to show that you asked the seller if there were any known or hidden defects with the caravan, and the dealer's responses? Because if you did not ask, the dealer is not obliged to tell you!
By all means talk to the dealer about it. I don't think you will get a FOC repair, but you might be able to swing a deal such as dealer pays for parts and you pay for labour or vice verca. I am certain tring to use SoGA would be an up hill battle with little chance of success. I susspect you will spend more money and time for no outcome, and you will almost certainly sour your relationship with the dealer. I think you'd be better biting the bullet and paying for the repair and putting it down to experience.