I must admit I thought dealer demo kit were assets held by the dealer. In my experience assets are depreciated for a business over typically 5 years from an accounting point of view. Therefore an asset used as a demonstrator 1 year old will already be written down by 20% by the dealer. Certainly with my dealer, this is a consideration for 1 year old demo kit and seems to often work for both parties.
If the assets are bought to be retained for use in the business by the business then they are "non-current" assets and will be treated as you describe for the financial statements. If the kit has been bought with the intention of selling it then it represents trade stock in "current assets" and should be shown in the balance sheet at the lesser of cost or realisable market value. The cost to the dealer is presumable somewhere around 70% of the retail price ex-VAT - so with a customer discount <= 30-ish% the dealer is giving away part of his retail margin.
Doesn't make any difference really though does it? If Halibut can find the same kit £400 less then the OP's choice is relatively straightforward.
