where I currently live most utility cyclists are going at 10-14mph.
I have not seen many drop handlebar bikes going fast, other than what appear to be middle aged and retired people training for races etc..
I do remember a few more more "faster" utility cyclists in Reading, but I got the impression many of them were actually quite agressive (rather than assertive) - saw one actually order a young lady (on a shared use path) to get out of his way rather than slow down..
he was too quick for me to catch up with him unfortunately (maybe just as well) I actually wanted to report him to the plod - that is the only time I've felt so angry I wanted to "grass" on someone.. this wasn't a young chap either, he was easily in his 40s...
however where I live now I once had a old man tell me "mind how you go boy" (in the local accent) because he felt I was
walking too fast, and a popular car sticker says "Don't rush me, I'm from Suffolk"
People here are prepared to accept a slower pace of life which isn't a bad thing IMO..
also I do suspect some "fast" cyclists apply the same leeway to their speeds as anglers do to the size of fish they have caught
With regard to plating etc the Powacycle Salisbury has a voltage/wattage plate (26V/200W) also marked "Zheijang Fujiyang Bicycle Company" (a place just SW of Shanghai)
Given that Powacycle's parent company is a major supplier of IT solutions to the education, legal and public sector market I can understand why they wish to play safe with regulations..
That said in the present climate I doubt if what is a very gentlemanly bunch of people getting a few extra MPH out of their e-bikes will attract much attention from the local constabulary, unless they start riding in a dangerous or anti social manner (which is equally illegal on a unpowered cycle anyway)
My experience in my youth of "bending the rules" in this country is that there is a actually surprising amount of leeway until things start going pearshaped for wider society, then there is a knee jerk reaction and the authorities tend to step in and increase the burden of regulations/enforcement...
Af course if things change in maybe 5-10 years time and modified e-bikes start posing an actual road safety hazard the situation could get worse for DIY'ers. Wasn't one restriction on motor power in either China or Japan due to concern over illegal mods and an actual rise in accidents involving e-bikes?