Point is sticking any of those engines on the DH 77 would have been a rather difficult task.
BTW the engine used on the P-26 weighed a whopping 715lbs.
Hispano Suiza 12X engine about 815lbs with supercharger.
Hispano Suiza 12Y engine about 1034lbs with supercharger.
A lot of progress was made in the years between 1929 (first flight of the DH 77) and 1934-35 (design work on many of the monoplanes of WW II) and no one feature could really show a dominant effect for several years. You might have a plane with a low drag wing set up (cantilever monoplane)
That is handicapped by a poor engine installation (not even a Townsend ring) or other not so advanced feature. This made it hard to pick out the really useful features,
You had influential people in England convinced that Biplanes outclimbed monoplanes due to greater lift (in theory, there were very few experiments to test it) and it took awhile for the theory (provable) that the lower drag monoplane actually climbed faster due to a higher surplus of power.
Compound this with the fact that all the smaller airforces what proven machinery, either engines or airframes and don't want to be funding experiments for larger wealthier countries.
The two lightweight British monoplanes of 1929-30 were pretty much dead ends due to size and inability to demonstrate significant performance advantages (in part due to other problems than the wing)