Exactly, Andy 👍😉
Because I just looked at your scdb.txt for England; the speeds are given in mph.

If you mix that with other km/h data, you end up with a mess that doesn't really fit any regional setting.

Spoiler: this one as an example

scdb.txt: -3.318560,51.651750,35,50,0,0 (51.65175, -3.31855) is originally listed as 50 mph, but would be displayed as 32 mph