Okay, this is going to sound very weird, but hear me out.
OTL, the Kuomintang ordered a dozen submarines (and a few other warships) from Germany, with the plan that they'd get delivered over the course of late 1937/1938.
I don't know who was going to crew them, but I imagine, judging by the role of German advisors in the Chinese military at the time, that the plan was to have Chinese crews and German officers.
Presumably, if Britain caught wind of this, they would be somewhat concerned about Germany testing submarines against the economic lifeline of another island nation.
Would this have had any political effects in Britain? Or is it too insignificant to be noticed?