Hi all,
Just wanted some advice on how to proceed on delay compensation and downgrade compensation claims.

14th April - BA60 was originally planned to take the longer route from MLE to LHR avoiding Iranian/Iraqi airspace, but one of the three pilots went down with food poisoning overnight so due to the flying hours limit of the remaining 2 pilots we had to land at LCA and switch aircraft with a new crew. BA scrambled an Airbus A321 Neo to Cyprus earlier that day to pick us up (new flight number BA667) and we had to take an involuntary downgrade from club to economy to squeeze everyone on board for the remaining 5 hour flight.
Eventually landed at LHR 4hrs 15mins later than the originally scheduled BA60 flight and were advised by BA via email to put in claims for compensation.

I put in three claims:
1) Delay compensation - claim rejected due to crew sickness being an extraordinary circumstance. Not entitled to compensation.
2) Downgrade compensation - claim has been accepted and they have offered £300 cash or £400 evoucher per person. Given that we had flown half the inbound in the cabin booked, is this acceptable? We originally paid 150k Avios, £1720 taxes plus a 241 for the return flight in Club.
3) Seat Reservation refund - we paid £178 to reserve seats for this leg. Claim has been accepted but refund amount has not yet been confirmed.

This is BA's response on the delay compensation point:
As your flight was delayed due to a member of the cabin crew reporting sick and wasn't well enough to operate the flight, and this then meant the crew operating hours were limited for the remaining crew. Because Male isn't the main airport we operate from we didn't have a standby member of cabin crew available. This means you’re not eligible for compensation.

Article 5.3 of the EU Regulation 261/2004 and The Air Passenger Rights and Air Travel Organisers’ Licencing (Amendment) (EU Exit) Regulations 2019 states a carrier is not obliged to pay compensation if it can prove the delay or cancellation is caused by extraordinary circumstances, that couldn’t have been avoided even if all reasonable measures had been taken. In Recital 14 and 15 of EU Regulation 261/2004, extraordinary circumstances include weather, strike and the impact of an air traffic management decision which gives rise to a long delay. This means you’re not entitled to compensation under the EU Regulation for your delayed flight.

I did not think I was being unreasonable in pursuing this as BA advised passengers to claim for compensation on the day of disruption. How best to take this forward?

Thanks in advance.