I fully support the advice you have been given about getting a damp report carried out with notes about the recent dry spell. but I think I should also make the point that the chances of getting a remedy against the repairer is not guaranteed, for one or more of the following reasons;-
Virtually all makes of caravans seem to suffer some issues with damp. Some manufacturers have a worse record than others for certain issues, and Avondale are not rated highly in this respect.
The original repairer would have been contracted to carry out certain works, How those works were specified is important. Were the instructions to the repairers to " repair the damp issue" or to "prevent further damp occurring"
If the former was the instruction, then the repairer was only obliged to repair the affected area without fully examining the rest of the caravan for other potential leak points. If the latter was the case, then the repairer may have failed in their execution of the contract.
You must also appreciate that its often the case that when a repair is carried out, its usually installing new materials next to original (aged) materials. Sometimes the repair is fine, and its the original materials next to the repair that deteriorate more quickly and start to fail.
If these are parts the repairer was not contracted to touch, they have no liability for their failure.
Sadly I unless there is a very clear failure of the repairers previous work, I don't hold out much hope of any remedy in your favour. I suggest not just having a damp check but try to get the surveyor to offer a professional opinion in writing as to the cause and if its down to faulty repairs or original structure.
You will have to decide after the damp check if its worth the time and effort and outlay to pursue a remedy when there is a reasonable amount of doubt as to the success of a claim..