From a BAEC email I just got…

An escape with a difference
Ready to hit the beach? The Sharm El-Sheikh flight departs from London Gatwick on Friday 03 November, book now and you’ll be among the first on this new kind of flight.

Book a return in Euro Traveller from £1 + 27,500 Avios, or Club Europe for £1 + 48,500 Avios, and with plenty of availability on return flights you can choose to come back on a day that suits you.

… I’m not at all sure they’ve thought through the number of seats. 180 Avios seats out would suggest that they need somewhere around 20 Avios seats back every day if people stay 5-10 days.

EDIT adding info from rhysflies on HfP…Whilst there is no dedicated Avios-only flight on the return, British Airways told us that they are increasing the number of reward seats on return flights on 6th, 8th, 10th, 11th, 13th, 15th, 17th and 18th November so you should have additional flexibility and choice when coming home.