A further comment on PlusBus - when booking train tickets online, if I book two tickets for me and my husband, but only want one PlusBus ticket as he has a pensioners' bus pass, I have to book the train tickets in two operations. Doesn't make much difference on the services I use as they don't give seat allocations anyway, but for those TOCs that do, it could be a nuisance as there's a chance of getting non-adjacent seats.
Also sometimes the Eastcoast website doesn't offer a PlusBus ticket at all, so on those occasions I have to cancel my order and re-do it on the ATW site. It seems quite random as to whether Eastcoast offer them - it's always the same journey, usually same days of the week, yet sometimes it offers me a PB add-on and other times it doesn't.