The volunteers will be trained to the same standards of SEP, security and Avmed as the current crew. There will be no drop in standards on those fronts. The CAA will be monotoring these courses and so I'd imagine that the SEP instructors may even tighten up on the standards. There will be less emphasis on the customer service side of the training, but that is because there will be a reduced service. All the volunteers will be happy to be there and so I'd imagine that there will be plenty of smiles to go around. There will be experienced crew on all the flights to deal with the more complicated cabin service issues.
All the above is my own views and opinions not BA's.