Thanks for the replies all. To clarify:
This is a ticket booked purely with Avios via the defunct travel programme and the upgrade is using a Lloyds voucher to go from PE to Club.
The change being requested is a date change. I have been speaking to Avios travel programme agents who will still administer changes to existing bookings.
And @
Globaliser yes you are correct - I'm trying to figure out if there are different rules applied to pure BA Avios bookings, and those that were originally booked under Avios travel.