It's easy, with our contrarian tendencies to focus on exclaiming why something would not, could not or should not have occurred. The trick is considering how to reasonably overcome these challenges. Focus on the how, not the why not.
OK, let us assume that some British company (Tommy's tin whistles, LTD) signs a deal with P & W. Now the question to be answered are WHEN. As in which version of the R-1830 because it was undergoing constant development.
The First commercial plane to be certified with the R-1830 was the Marin Clipper on Oct 9th, 1935. Engine maxed out at 2550rpm for take-off at 950hp. Supercharger was pure crap.
At 2400rpm max continuous was 830hp at 3600ft.
The 2nd commercial plane to be certified with the R-1830 was the DC-3A on Nov 28th, 1936. This version of the engine could run at 2600rpm for take-off and 2450rpm max continuous. Supercharger was still crap but a higher supercharger gear allowed for 900hp at 6000ft. Engine gained 75lbs.
The C series engines show up a bit later and they will run at 2700rpm, a larger supercharger offers 900hp at 11,000ft (supercharger has larger impeller and turns slower than the old supercharger). Engine has gained 113lbs. For TTW, Ltd, all of these engines will run on 87 octane fuel, which might be important in 1937-38. These are the engines the French bought for their first Curtiss Hawks and for their own Bloch fighters. The 1200hp engines used in the Australian Beauforts don't show up until later.
Saying somebody could have made a different decision is one thing, asking for a time machine is something else.
Also important as the why we can consider Alvis. A competitor to TTW, Ltd, Alvis signed a deal for the range of G-R engines in 1938 and started looking for business from the Air Ministry. Rightly or wrongly the Air Ministry did not to deal with another engine company. Alvis, not being completely stupid, only built a small factory (large shop) capable of truing out 15,000hp worth (?) engines a week as announced in the aviation press of the time. Now if they are making only 14K or Ns that is under 15 engines a week at max capacity. They never got any orders and did a lot of overhaul work and subcontracting. They also greatly expanded the facilities.
Getting back the when. The later model R-1830s used very few parts in common with the early engines.
The Australians put "foreign made engines" into their Bristol Beauforts.
They used both and Australia was not happy with the way the British treated them both before and during WW II.
It also took several years for the Australians to make R-1830s in Australia. It was not a matter of political will. It was also a matter of getting the needed machine tools and equipment and training a work force.
This is something many politicians refuse to acknowledge. You can't build and equip factories in just a few months and you also cannot come up with a skilled workforce in just a few months. You can, at times reduce a work force and keep a cadre of workers to help ramp things up if needed but it is very hard to start from zero.