There is one simple, although not 100% reliable method of checking a company's solvency, and that is to do a simple search using one of many firms available. Here is one that I use to run checks on competitors:
Free company financial check on WHITES CARAVANS LIMITED and free company accounts
You will see that this firm's net worth has gradually deteriorated over recent years. It doesn't mean that they are going bankrupt as they may well have an excellent line of credit from the bank and many companies trade honestly and successfully when they have assets of say £50K but a bank overdraft of half a million. What matters is their profitability and you can only get that by paying for a full report and even then, small companies such as this do not have to disclose their full accounts.
I do wonder though how a company such as this can only have liabilities of £14K. I would have thought that they'd owe their suppliers much more, especially in a business with such high value products.
Now a rider: They may well have another trading company and this one could be, for example, the accessories shop part of the business, or it could be that the sale of 'vans is a separate partnership and not a limited company. However, I've checked their website and the name listed there is Whites Caravans Ltd. which is what I've searched on.
So to sum up, they may well be eminently respectable but I would not be leaving a big deposit just in case. If a deposit is essential, talk to your solicitor about putting it into an escrow account just in case anything untoward happens.