The eighteenth century pre-dates the national censuses that started in 1841, so your best hope is property records. There was not at this time any systematic recording of land ownership (the first national return of Owners of Land didn't take place until 1873) so you are reliant on records of property-related taxes, of leases and rentals, and of the transfer of property rights at death (via wills) or as a commercial transaction. Any of these might name or describe the property in question.
[Note: There were some local censuses and Population censuses before 1841, but the population censuses didn't record the level of detail you're looking for, and I can't find any reference to a local census for Oldbury-On-The-Hill.]
Your first step should be to search the catalog at Gloucestershire Archives, looking for the name of your person of interest and more generally for Oldbury. This may throw up wills, rental books, leases, conveyances, land tax records (and possibly other records that mention the property in passing). I don't believe there's any material from the archives online, so you may need to visit in person to review the records or pay for some research there. (You may be lucky and find the catalog entry provides the detail you need).
Should you locate a description (or with luck, a name) for the property, your next challenge will be finding it on a map. Properties and places changed names more often than you might expect. Again, Gloucestershire Archives are your best hope -- the tithe map might be a little late (circa 1838) but you should check it anyway; Gloucestershire also (from the catalog) have a 1755 "Map of central part of parishes of Didmarton and Oldbury-on-the-Hill" but it may not be detailed enough or show the area you're interested in.
One wonderful resource that is available to the academic community but not us non-academic family historians is Historic Parishes of England and Wales : an Electronic Map of Boundaries before 1850 with a Gazetteer and Metadata which presents data based on a variety of historical sources and can be a good aid to locating properties. (I would love to be able to get access to this).
Other options to explore: Newspapers and property transactions by Ozias Linley, who inherited the property in question. Ozias's willl was proven in 1831 and is available at The National Archives. If Ozias has no children, you'll also need to look into the will of William Linley, who would inherit the property in those circumstances.
Edited to add: Knowing the chain of inheritance makes the Tithe Apportionments much more valuable -- to the extent they may answer your question directly. The 1838 Tithe apportionments (online for a subscription at TheGenealogist, without -- alas-- the maps until later this year) show William Linley renting out a 'House, Garden and Buildings' (ref 200), a 'Paddock' (ref 198) and an 'Inclosure' (ref 33) in Oldbury on the Hill to Joseph Holbrow. The Tithe apportionments (series IR29) and associated maps (series IR30) are available at the National Archives as well as at Gloucestershire Archives (which will use different references). Of course it's possible that Ozias and/or William sold or bought property in Oldbury under the Hill after their father's death, so the property owned by William in 1838 isn't guaranteed to be exactly the same as his father owned, but it's likely that it was.
Once you've consulted the tithe map to determine exactly where the three pieces of property were, you'll need to try and locate them on a modern map. Don't be surprised if the buildings no longer exist or have been altered significantly.
