I consulted my partner (who is a lawyer) about all this and funnily enough the Ainsworth vs Lucasfilm case is a textbook case for intellectual property law in the UK. Her view was that it is a bit of a 'grey' area, and the Ainsworth Case doesn't mean that the UK is wide open to prop making at all. The distinction is as OCDChad sort of says, there is a difference between Copyright/intellectual property and design right. In this case, for it to fall in the copyright category, it had to be considered to be a 'sculpture'/'work of art', which is what Lucasfilm argued. However, the Judge said it wasn't (though perhaps I'm sure we'd all disagree...) and said that the original purpose of this was not to be a sculpture, but a costume, hence design and hence it had expired.
Both design right and copyright are automatically granted (I believe) for different periods of time, but to solidify this, they usually have to be registered. Anyone can go on the Gov.uk website and search for an item to check it. However, it's such a grey area as to what something is and isn't. For example, 'Sonic Screwdriver' is a registered term, but the designs aren't registered? They change and fluctuate and they aren't copyright at all. Still i'd be cautious parading round selling these bits, especially with skilled people who are licensed making them.
With Star Wars, all the items were broadcast to the world before they could be copyright registered, but they all had design right in the UK/EU. Can't copyright the 'Stormtrooper' name as that was kicking around in Germany 40 years previously, so what's left to be registered?
So the answer to the question: Can anyone make any Star Wars prop he wants and advertise and sell it as such if it's been 15 years since it was first made?
Well, yes and no. If in doubt, contact Gov.uk and check the registers. OT Lightsabers, probably, Stormtroopers, probably, E-11s, probably, Any stuff from the recent films, probably not! As always, be cautious with these things.