It sounds to me as though this is not about a ticket refund, but rather an EC 261/2004 claim for duty of care, e.g. the hotel room and perhaps meals and local travel. If that is the case, there is no chargeback issue, but rather a reimbursement of out-of-pocket,.
At 33 days, it is hardly "shocking." I would expect 60-80 days at a minimum. You may well find pushback from BA if there were later flights available and you simply chose to spend the night.