I appreciate the collective wisdom in response to posters who have problems with their purchases. I think it is important to consider the relevant legislation when things go wrong. The Consumer Rights Act 2015 has overtaken the Sale of Goods Act 1979.
The Act requires goods to be of satisfactory quality, fit for purpose, as described, and last for a reasonable time.
Your rights under the Consumer Rights Act are against the Retailer, the Company that sold you the product,
NOT the Manufacturer.
Customers may lose the right to a refund if an item is damaged by trying to repair it themselves, or getting someone else to do it. (There may remain a right to a repair, partial refund or replacement.)
I would reiterate my suggestion to contact The Retailer who was contracted to supply the boat/trailer/lighting board. If they were supplied from new, this is likely to be Swallow Yachts. I consider it an essential step to ensure contractual obligations are observed, and to highlight quality issues which can then be addressed.