Yes, it's just a key route for BA, in fact the key route,. and no they generally won't cancel services. It can happen, but generally speaking BA will run those services and they are often full. They cut back a bit over Christmas and Thanksgiving and maybe Labor Day. I've heard people being taxi'd off to Newark when there are no spare seats left, more a factor in WTP than CW. If you don't reserve seats then yes, you are likely to get a central pair and because Club Suites are so much alike, there really isn't much point in reserving in CW, Even in the middle pair you will be somewhat cut off from everyone else including your travel partner.

Note the day time flight which deals with the hotel issue at the LHR end.