The UK has (and had prior to Brexit) its own national bus vehicle Regulations (national small series) - I believe Ireland will also have a similar opt-out, which means that the standard double decker bus here in the UK and Ireland can't be run in Europe - double decker buses in Europe
must have two staircases. The British Isles have specialised into deckers, Europe into artics. Passengers in the UK and Republic of Ireland generally pay something like the full cost of bus travel, Ireland has PSO bus routes which are subsidised, and the UK has supported services but neither country really has a low-fare policy subsidised by the local or central government.
The UK's and Ireland's buses are really designed to maximise revenue & passenger seating (I usually get city buses on the continent, and I usually have to stand, but there it isn't particularly noteworthy, unlike here), and minimise public expenditure. This (and fraudulent personal injury lawsuits) is why exit doors are only found on the TfL network, where fare-dodgers are TfL's problem, not the company's. More doors speed loadings, but mean fewer seats in the lower saloon and greater chance for fare-dodging. The trade-off seems to be "You'll either be standing, but hopefully on a shorter journey, or it'll take longer, but there's a 95% chance you'll get to sit for the whole journey".
Buses in Europe are mostly directly bought by the public sector - this means that EU public procurement (
lawsuit inviting fair, open and transparent) rules apply, or indirectly through the franchise/concession model which produces the same effect. UK bus
companies on the other hand can buy what they actually want. UK companies can build up relationships with their supplier, and negotiate accordingly - whereas transit authorities have to know
exactly what they want and pray
the competent the best supplier writes the best tender bid.
European manufacturers offer a highly standardised "off the peg" bus, whereas UK manufacturers are much better at accommodating creature comforts like seating with padding, recessed lighting, grab rails in colours other than grey, slightly longer, taller, or shorter vehicles and other details like that. The number of doors in the different places is a red herring IMHO, as is the LHD/RHD issue as vehicles don't have mechanical pedals/steering systems anymore - they're all electronic now and could theoretically be sited anywhere in the vehicle as long as type approval regulations permitted.
TL

R UK and Ireland have made several policy choices which are completely different to Europe. This means our respective buses look radically different.
I would like to know if i'm the outlier who thinks that bus journeys in the UK are usually more comfortable than in Europe - purely because you can be reasonably confident you'll get a seat. I also wonder if anyone disagrees with me when I say that buses in the UK and Ireland feel less "government-issue" than abroad. Although I do remember buses from decades ago which were very much "here is a box on wheels and we've filled it with formica - what else do you want??!"