We wouldnt usually hold the avios seats because the system we have only allows you to hold the availability for One flight in one booking class.
You see it means that if you didnt want to go ahead we would have lost the orginal fare and would potentially cost ba to put that right.
However what i would expect and what i would do in this situation is call up the fares department and explain that there is limited availability and if they can do the quote over the phone. This is something they will allow particularly if its Uua.
Its usually only send down to fares if the flights are more than a few days away and you are looking to change to flights on a different day where we can then hold the availability.
***** all opinions are my own and dont represent ba or iag***