I will assume you contracted to purchase the caravan after October 2015, in which case your legal rights are defined in the Consumer Rights Act 2015.
I suggest you google it or look at various consumer rights web sites like, Which or Moneysaving expert etc.
Whether you will be liable for any costs or whether you will loose your deposit will depend if the seller has broken the contract you agreed.
If you stipulated when you agreed the contract to purchase that the caravan MUST be delivered by a specific date, otherwise you would not purchase, then that would be defining part of the contract, but I suspect that if you had made such a stipulation the dealer would have countered that by stating they could not guarantee a delivery date, and if you had insisted on that element the dealer may have withdrawn their offer to sell.
I should point out that most caravan dealers contracts will ask you to accept there may be delays in delivery when the cause is beyond their direct control, such as manufacturer's production or delivery schedules. The fact you went ahead and ordered it would mean you would have accepted that flexibility as part of the contract which you signed.
As for the level of service, that is tricky one; We often have misbeliefs about what service is acceptable, i.e not falling below minimum standards, but the problem is; there are no minimum legal standards for retail selling, except that the service must be as described, fit for purpose, not fraudulent and must comply with any relevant regulation (if any apply to the nature of the service in question).
Essentially you would have to show the dealer is abusing their position of trust, or are discriminating against you. You may need to seek advice from trading standards.
Before you take any precipitous action, look up the CRA and check out the advice from reputable organisations such as those noted above.
With a pinch of honesty compare your experience with what you find there and only if you genuinely feel you have been wronged, then consider further steps. I suggest that you should write to the dealer's MD and lay out your concerns and how you think the business has failed you. Ask him/her to respond. You never know there may be some very good reasons why your purchase has been difficult, and who knows there may be an offer of compensation. If the response is not forthcoming, or it is unacceptable to you, then look to take it further by invoking one or more of the CRA's criteria.