Apologies if your already aware but according to ba.com you have to inform BA your taking a bike. More info here and 13901 has good knowledge of such things.

https://www.britishairways.com/conte...orts-equipment

What size bike can you bring?

We need to know how big your bike container is and how much it weighs.

Your bike can be transported in a hard-shell box or padded bike bag up to 190 x 95 x 65 cm (75 x 37.5 x 25.5 in).

A bike box or bag is considered an oversize or out-of-gauge bag. You’ll need to check your bike in and drop it off at the airport out-of-gauge bag drop at least 90 minutes before your flight departs for it to be more likely to travel with you.

Let us know you’re bringing your bike

As soon as you’ve booked your flight, let us know that you’re bringing your bike by using the online chat on our Help page.

Please do this as soon as possible, as some flights are very popular with cyclists. Your bike is more likely to travel with you if you tell us in advance, and at least three days (more than 72 hours) before you fly.

Travelling with your bike

Please ensure your bike is clearly labelled with your details on the outside and inside of its cover or box, preferably fastened to the bike frame.

Clothes and other personal items must not be packed in your bike cover or box. This may cause delays during security screening or mean your bike cannot travel.

There's a few threads on it too. I remember this one which I thought was a good read.

https://www.flyertalk.com/forum/brit...dvice-log.html