As mjh0 says, I would guess that BA have signed contracts for a significant portion of the refurb [seats and labour] already. With the supposed manufacture limit they can't really speed up while they have idle frames either - though if they're happy with their long term outlook they might try to do so as it would mean not having the aircraft out of service during a future period when it could be productive. That would be down to the seat manufacturer though - I don't recall seeing whether the "3 a day" was just the initial maximum production rate or a long-term maximum. Of course, global supply chain is also seriously compromised so who knows what each of these companies is capable of right now.