It can be exceedingly hard to get hold of any bus at times, let alone of one suitable for every passenger, but to be fair it always seems to me that there are just as many decent coaches as bad ones used on emergency/ad-hoc replacement services, perhaps excluding Redhill-Tonbridge.
I'm by no means a bus or coach fan when it's put in comparison with a train, but a lot of the time GTR use the likes of Crawley Luxury which, though perhaps not always living up to the second bit of its name, won't cause much discomfort at all!
On the other hand, a lot of the more accessible buses are used on timetabled RRBs during engineering work, which are probably needed to ensure formal plans have been made for those with such requirements; however, these are often double-deck tin cans more suited for 5 minute hops around South London, and by no means comfortable enough for most people to endure on a longer run like Redhill to East Croydon in a crawl on the A23!
I'm amused by the fact that it has window curtains. Not sure anyone's getting much sleep on one of those...