And that a "mandatory" cycle lane ISN'T mandatory for cyclists, it just excludes all other traffic (if I read correctly). Somewhat confusing terminology!
As to the minimum width of 1.5m - the "cycling town" of Aylesbury painted some so-called cycle lanes a few years ago (now mostly worn away by vehicular traffic, parked over / on etc. etc.) that were well under that, and probably under 1m wide over their whole length.