Just booked this fare through worldairfares.com for flights in August and ensuring I fly on Finnair's A350.
Finnair prices were £550 (no hold luggage), BA over £1K.
Booked yesterday, expecting to hear that fare is no longer available blah blah but sent an email asking if the booking request can be honoured and within 60 minutes received BA booking code- result.
Generally I don't do 3rd parties but thought this was a risk worth taking. Fare also being offered by Travelup a few pounds cheaper but I would only use them as a very last resort.