I might jump in here. I learned to drive on my father's 1956 Morris Oxford, pretty similar to the Austin in those pictures, and while it was certainly not a high-performance car, it was typical of its period and price-range, and reliable. And yes, it had the oil-bath air cleaner. A mechanic, not understanding the function of the lock-nut (pair of nuts) on the top, screwed it down, bending the "lid" and closing off the air flow. The car would start and idle fine, but the moment you put your foot down, it reached a limit (perhaps 20 mph in 4th gear)! By the way, you shouldn't worry about the noise of 1st gear (straight-cut with no synchro-mesh) since it was intended more or less as an emergency gear; in normal driving you used 2nd gear to start, and of course although the power developed was low for a 1500 cc engine (by today's standards), there was plenty of low-speed torque. In fact the weakest point was the linkage for the steering-column gear shift, which would fall out leaving you in 3rd gear ... but with care you could start and drive almost anywhere in 3rd!
Ken G, 1925 Rover 16/50 (San Francisco)