I've been doing some more research, and I think these photos are of the fort at RAF Sharjah.
There's a good photo of the same fort in "The Sand Kings of Oman" - here's a link
Title half way down the page.
Here's a photo of the gates of Sharjah Fort from the page
Sharjah Fort entrance gate, the Trucial States (a lot of the pages at this site are missing their images)
The below photo is from the same site - RAF Sharjah from Sharjah Fort
Here I've blown up the gate of the fort from my post - interesting one has the cannon, the other doesn't. The layout is the same as the above photo, especially the slope of the roof, and the steps.
I think the clincher are the images on this page
Sharjah Airport | 40 years of the UAE an example of which is below.
