Source: CCHQ = Conservative Campaign HeadQuarters.
In reality, the Conservative Government is desperately seeking a Brexit "deal," an effort in which it faces seemingly insuperable difficulties and which, if it succeeds, will likely result in a deal having almost as many sovereignty denying features as Theresa May's thrice rejected deal.
The fact is trade deals are mainly about fixing things to the advantage of commercial interests with powerful lobbies and are of of questionable value to the public at large when they are not detrimental.
The UK, as the second largest economy in the EU is clearly of great importance to many European businesses and if a "no-deal Brexit" were to create significant UK–EU trade restrictions there would be effective pressure placed by EU entities upon the EU Council to negotiate relief from those causes of friction. Moreover, during negotiation about such restrictions to trade, there will have to be give and take that allows as much for British interests as they allow for EU interests.
Thus, the Brexit Party is absolutely correct in stating that they will support the Government in the event only of a "no-deal" Brexit, whereafter, Britain will have completely free hands to negotiate trade matters in a way that serve British interests without compromising British sovereignty.