The lack of FSD beta development in Europe isn't really down to Tesla
Without 1st hand insight to exactly what discussions are going on, it's impossible to comment on who is stopping / delaying who.
However, as per this thread, when there is so little if any sensible, consistent product evolution / improvement (tested, documented updates, universal application of new <working> features to all capable vehicles, honesty regarding radar / phantom braking, minimal regression with updates etc etc) it is hard to argue that Tesla is smoothly cracking on along the road to an FSD product that is likely to be acceptable in the UK. It feels more like the car's don't have adequate sensor suites even by Tesla's reckoning with no clear message stating how shortcomings will be addressed such that regulatory concerns are definitely not the issue stopping progress.
Regulators for UK surely have more than enough grounds to question the status of FSD and the whole development process given the path so far. Not helped by the spectre of an engineering team that does what takes its fancy. (Ref. Elon's tweets mentioned above)
The biggest concern for me is the apparent lack of attention to different markets. Ok, UK being RHD does put us in a minority, but if you sell in a market you should fully support that market. In any case, having driven my car in LHD countries, it wasn't significantly different and actually exhibited different anomalies on French autoroutes compared with UK motorways that suggested to me how the lane control design was very specific to US road conventions.
Tesla does not do itself any favours in the way it supports UK owners. Having lived for some time in SoCal I can clearly see for example why humidity in B Pillar cams and lights would not seem to be much if an issue, but here it most certainly is. A/C also performs well below other EVs I've owned relating to cabin humidity.
I'd agree with the statement that it is hard for Tesla to develop if they can't get testing in Europe. But look at FSD Beta progress and it doesn't give confidence that it is ready for Europe/ UK when the US development process is struggling. It really feels like Tesla is hiding behind the regulatory acceptance issue, rather than embracing its UK FSD owner base to garner support by showing its commitment and ability.
Even the claim that FSD cars are at least 'FSD capable' needs supporting evidence which so far I haven't seen.
I suppose Tesla's (attempted) move to VO could be another case of them trying to dodge any possible (very costly) obligation to upgrade hardware (again), in this case, radar, without which the car is arguably not FSD capable.