I've been told that BA have impoved some of the amendment options for Avios bookings.

1) Change Zone now allowed
This used to be a problem, particularly where one leg had already been flown, that changing to another zone was not allowed. If the flight had not been flown then cancellation and re-booking could be done if there was availability on all legs, which of course would problematic in many cases. Anyway that problem has now gone away, there is now an ability to amend an existing booking to change zones. See the Spending Avios sticky for details of zones.

2) Upgrades and downgrades allowed for Redemptions + Money
There was a similar issue with booking made with Avios + Cash bookings, again that inflexibility has gone and it's ok to upgrade or downgrade the booking, subject to availability in the new cabin and dealing with any cost differences (could be a refund in some cases). So this allows you to book something you can see/affford and change later if seats come up.

3) Change a pricing option
And finally, in the same vein really, you can amend an existing redemption booking to increase or decrease the pricing options.

I presume the usual £35 amendment fee will apply. I don't know many more details, but doubtless that will emerge in the the months ahead. As far as I know this has now been implemented, but it may take agents a week or two to be aware of the change.