I've dug out my kit and taken a few photos of the kit and the remains of the box art - Why do people put sticky tape across pictures (and then pull it off)?
Anyway, it's been good to re-familiarise myself with the kit, and might have been useful for anyone trying to identify other (Marinecraft) models.
Looking at the thick card box, I would assume that it was used as common packaging for any one of the four models shown on the label (2 x Sail and 2 x Powered).
The details given for the manufacturer and location on the box label are:
"Marinecraft" Kits
Model Aerodrome Ltd.
131, Stratford Road,
Birmingham, 11.
The instruction page provides a little bit more information;
"Marinecraft"
Model Power Boats
Designed by E.J. Pollard and produced by
Model Aerodrome Ltd.
131, Stratford Road, Sparkhill, Birmingham 11.
The instructions also give the basic specs for two models with 'Fibreglass Hulls';
The 'Oban', Fishing Cruiser. 27" OAL, Beam 7½"; and The 'Jura', Ocean Cruiser. 38" OAL, Beam 11½".
Details of the kit hull (which aren't apparent in the photo of the eBay example - see OP), are that the transom is trapezoidal, being wider across the botton than the top, and that the top and bottom edges are parallel and straight (No Vee).
The deck line is not straight (as it may appear in the posted image), it actually curves upwards towards the bow.
I also found that I had the original decals (with the name 'Jura') although I'll assume they will be brittle by now, although should be okay for scanning.
Images of (my) 'Jura Kit', Box artwork and other kits reference below...

Box Art Showing Manufacturers details plus 'Jura' and (presumably) 'Oban'

Instruction showing name of designer and full address.

Unbuilt Marinecraft 'Jura' Ocean Cruiser kit, in original (very tired) box.

Box Art (Left): FIONA MK II. Fibre Glass Hull. 36" length. 9" Beam. Ready made sails. Braine Type Steering Gear. Lead Keel and all rigging.

Box Art (Centre-Left): JURA. Fibre Glass Hull. 38" length. 11" Beam. Die Cut Ply Super Stucture, suitable for 3½ to 10c.c. Diesel or Electric. Suitable for Radio Control. Full detailed plan & instructions. Note: Image appears to indicate a cabin door and 'double' bow-rail, and hints at paint scheme.

Box Art (Centre-Right): (Presumably) OBAN. Fibre Glass Hull. 27" length. 7½" Beam. Die cut ply Super Stucture. Beginners Model 1½ to 3½c.c. Diesel or Electric.

Box Art, (Right): IONA MKII. Fibre Glass Hull. 24" length. 5½" Beam. Beginners Model. Easy to build.
Finally to clarify, I have an unbuilt 'Jura' kit, for which I would like to find futher information - See previous posts. The partially built 'Jura' is an example image, used for illustration purposes.
The information provided for the 'IONA MKII', 'FIONA MKII' and the 'OBAN' is provided as a record to assist anyone who may have, or acquire, one of these models because reference for 'Marinecraft Kits' is rarer than Rocking-Horse droppings.
Andy