In the video above, his girlfriend's 125cc was a race replica- uncomfortable and with a front brake that was more of an on-off switch compared to a 300cc Ninja front brake.
A 125cc 4-stroke is probably just fast enough for a 55 mph speed limit, but at a high rpm that will wear the engine out pretty quickly for hours at a time, and such a light bike will likely get tossed around more by wind gusts.
Some countries have a 125cc 2-stroke engine available for street use with about the same power as a 250cc 4-stroke engine.
A 125cc 4-stroke scooter might be very comfortable, but it is only for a 45 mph speed limit or less, and you will not learn how to shift gears while using a clutch lever. A beginner is helped by starting with an automatic transmission, then later learning to manually shift for their second motorcycle.
Soon you will not be able to buy a new non-ABS street bike in England, and BMW will soon only sell new bikes with ABS- their on and off-road models will likely have a switch to turn off the back wheel ABS when desired.
“Banking institutions have banished precious metals and substituted a more fluctuating and unsafe medium; they have withdrawn capital from useful improvements and employments to nourish idleness for the few, who prefer demoralizing pursuits to labors useful to the whole; the peace of the whole is endangered by evils more easily to be deplored than remedied." by Thomas Jefferson,1810 (edited)