I don't know about London specifically but with regard to cyclists I get the impression that bus and lorry drivers have become more careful these days for one reason: the growing number of cyclists with cameras mounted on their bikes or helmets, and in cities even more so due to the number of CCTV cameras that could also catch dangerous behaviour. Furthermore some buses in bad areas have their own cameras watching the road recording in case of dispute (hooked to the same recording equipment that records inside the bus to capture events where passengers attack each other or the driver).

The average bus and lorry driver always was pretty safe on the roads and courteous with it, of course. They haven't changed.

But there were a lot of idiots out there in all forms of transport who were not so careful and got away with it because "who was going to know?". If it came to an argument it was the cyclist's word against theirs and if it came to court they could threaten to sue for damage to professional reputation if the case was lost by the cyclist. Now with a helmet cam the cyclist has evidence so it isn't just word against word. In most jurisdictions a single helmet cam recording is not sufficient for a prosecution (and may even not be directly admissible as evidence in court) but more than one complaint is usually enough for the bus/lorry company to investigate further (which they will as there are potential fines for not and in some places that threat has teeth) and evidence from official CCTV and on-bus recorders is usually admissible (the former because it is operated by the authorities, the latter because the driver has consented to being recorded). If there is a chance you will get caught and successfully charged with dangerous driving (or the lesser offence of driving without due care and attention) then bad/aggressive/otherwise-unsafe drivers are likely to put more effort into being less bad as it can get them reprimanded by their employer, possibly sacked, possible prosecuted, and it can harm their ability to get driving jobs in future.

So the average carefulness of large vehicle drivers is improving because of monitoring, the perceived average even more so because we never notice the good drivers as much so the bad ones look more statistically relevant than they might actually be.

I have had a "near death incident" or two, so the situation is still far from perfect, but these days I see more complaints about large cars (SUV types and people carriers) and private vans, than buses or lorries.

I cycled through London (not the absolute centre) until a year ago and found the lorries fine, they're courteous and give you a lot of space (much more than the buses, who were worse than cars - cars would give you space, whereas buses seemed to pretend you didn't exist). Worst of all was people-carriers, especially around start/end of school hours.

The pedestrians here terrify me. Cyclists get a lot of stick because there are a few bad apples that ignore red lights, but I'd say the vast majority of pedestrians don't give a second thought about walking into the road on a red light. The worst time for me is when I'm cycling past a stationary queue of cars and people assume that because the cars aren't moving, that nothing else could possibly be travelling along the road!