I've booked the Multi-Leg trip below...

DUB>LHR
LHR>KUL
KUL>BKK

I'd be interested in upgrading to F for the outbound LHR>KUL leg, at the moment when I go into 'Upgrades' on my Booking, it says that I need to phone British Airways if I want to make any changes to my booking.

Is it likely that a POUG might become available later in time, or is my booking potentially just not going to be eligible for any type of upgrade?