I can't comment on what you are entitled to but had a problem with BA out of London to Bangkok two years ago. They had 'overbooked' the flight. Managed to get us on a Qantas flight later that day but then lost our luggage for three days in the process of the change of flight. Lots of stress and annoyance at the start of what should have been a lovely experience.
Wrote to their BA customer complaints department and had an acknowledgement of the complaint within about four weeks later and a warning that they had a 'backlog' of complaints they were handling (as if I cared about their problems!). Took them TEN MONTHS to reply with a cheque for compensation. I think they gave us about 1/4 of the price we paid but I was astounded that a company of their size took so long to respond and compensate. Appalling!
If you believe you are entitled to some compensation, write, emails, write, email a LOT and you will eventually get some kind of response....Good luck.