I thought long about replying to this thread but thought it might end up where it did, shame.

Pilots and cabin crew at BA have different agreements with BA as to the minimum standard of hotel that is acceptable, these are agreements made with the respective unions after long negotiation. Sometimes (often) the hotel used can accommodate both sets of requirements. When this is not possible you will find pilots and crew in different hotels. The other reason for different hotels is that hotels cannot always, or are unwilling to, guarantee enough rooms per night, and so the crew gets split up.

Upgrades can be for strategic or tactical reasons. As a large number of rooms are taken, the hotel policy will often dictate that upgrades will happen, if this is at the strategic level, is when the contract is signed the rooms are allocated by rank onboard, first Captain, First Officer then CSD etc. At the tactical level, upgrades happen when the hotel can fill it's "traveller" rooms with bookings from non airline staff, but not it's "club" or "first", then a tactical upgrade happens and, usually the same order of upgrade happens, but again this is dictated by the hotel.

Personally I dislike cabin crew being in a different hotel to the flight crew for many reasons but it happens.