The 400MMC buses Reading have need to have the ignition switched on about two minutes before the engine has started to reset all the electronics, including the heating. A common problem was taking over one of these vehicles where the heating wasn't working because the previous driver hadn't reset the bus bus first thing in the morning. This would then require delay where you had to switch everything off including the master switch and then switch it all back on allowing time for the electronics to reset. This could cause about 4/5 minutes delay which, with the tight running times R.B have, could mean running late for the rest of your shift. Cold bus on time or warm bus late was the choice. It's worth noting that this reset always worked.
Cheers
Don't know about the heating.
FK▸ new vehciles seems to auto start with the heating on auto at the outset.
However, anything to do with a master reset (switch off everything and wait..) will involve many minutes delay which will add to your already late running as there is NO spare in runs. You might be lucky to have perhaps a 10 minute turn around at one end of your run, but if you arrive 10 minutes late, there is no layover.