Modern Vespa

In my area we are still at the crossroads transformation (with traffic lights and without) into roundabouts and the traffic is safer and better; other improvements are the bumps (very high and hard) before and after entering the schools. Those with more students have local police officers and / or volunteers but this has only been around for ten years.
The canalization is almost impossible, the roads here are narrow and I think it is still a good solution but the imponderable risk always comes from the driver.

In Guatemala they are not illegal, traffic is crazy with tons pf motorcycles and scooters splitting. I normally do filtering only.

Filtering is mentioned twice in the 2010 Highway code (the last copy I have) - IIRC that was the first year it was mentioned, but only as a warning for car drivers to 'be aware of motorbikes that may be filtering'.

e.g rule 211:

You are quite right in that the HC doesn't mention either lane splitting of filtering explicitly but this passage seems to show acceptance to both implicitly

Rule 211 (old 187) - "When turning right across a line of slow-moving or stationary traffic, look out for cyclists or motorcyclists on the inside of the traffic you are crossing. Be especially careful when turning, and when changing direction or lane. Be sure to check mirrors and blind spots carefully" has been added.

I definitely would not commute in the UK if I couldn't filter/split.

My current commute takes 12-15 mins on the scoot - public transport takes an hour and in the car it can be anything from 30 mins to over an hour

You have to be extremely aware though - fingers crossed I've never had an issue but one or two close calls when idiots have suddenly decided to move for no apparent reason.

Over 15-20 mph I wouldn't bother splitting and even below that I am very careful making sure I only split cars that have another car on their right and not a space they could be tempted to move across into.

This ^^^^

You ride by watching how the gaps flow more than watching the cars.

I actually watch both, as well as other, faster, riders coming up from behind.