Just from the bulb ratings, these sound like they could be a product of Noma UK - a manufacturer who are still going today, and who have been producing lights for the UK market for decades. No fitted plug suggests being sold in and around the 1980s, as before then, a lot of decoration light sets were supplied with bayonet lamp-base plugs, and I believe double insulated wiring was introduced at the beginning of the 90s. Any chance of seeing some photos?
As a collector, I would certainly be interested in one (or two), but have no idea what their value could be. Typically the small-bulb sets do not fetch as much as the old larger 12-bulb sets do, except in the case of rare and collectible lights such as those produced by Pifco, which are routinely fought over by us collectors. Don`t know why, but Noma-UK sets never seem to attract quite so much attention in comparison. Mint boxed sets should attract a better price than normal of course, and there will certainly be an interest among collectors..
As for legality of sale, I see Ebay auction descriptions quite frequently referring to "the plug has been removed" and "consult a qualified electrician" implying that they should be sold as non-functional collectible items only, and not for use unless checked by a professional. This can be quite frustrating for the collector when an original factory-supplied vintage plug gets removed, but is understandable from the seller`s point of view. Thankfully not too many of the really old sets have their old bayonet plugs removed, and as you say, these ones have no plugs to begin with - so long as they are sold as collectibles only, there should be nothing to worry about..
