is this booked as one flight through BA or as two seperate flights?
Edit:
https://www.britishairways.com/trave...k/public/en_gb
We have partnerships with other airlines to offer you more destinations worldwide, so even if you've booked direct with British Airways, one or more of your flights may be operated by another airline.
If your booking includes flights on an airline other than British Airways, your baggage allowance may differ from the British Airways allowances shown.
When checking in with another airline, additional baggage charges may apply.