reet, here goes.
The majority of the rear wheel covers, which were logo printed by the individual dealers were made of a PVC/fabric combination or similar. It fits over the rear wheel using an elasticated ring around the back of the cover, so it is all held snuggly in place.
If you do a search on here about tyre sizes, you will eventually come across the following suggestion about wheel sizes. I appreciate this is somewhat of a sweeping generalisation, and there are lots of infinite details to watch out for, but it does explain how one size fits all.
AN EXAMPLE:
A 15" wheel on a freelander will be fitted with a tyre with a relatively high sidewall, that is the distance from the tread on the road to the outer edge of the wheel rim. A 16" wheel will be fitted with a tyre which has a relatively smaller sidewall, thus the distance from the tread on the road to the outer edge of the wheel trim is less.
Critically, the outer circumference of the tyre fitted to the 15" and 16" is quite similar, provided tyres of similar aspect ratios are fitted.
Thus the wheel cover, being elasticated, will fit any wheel 15" or 16". (within reason)