Upgrade availability on VS019

Hi
I'm booked on VS019 in Premium Economy for a flight in mid-June. A friend of mine who works with Virgin has got me on the priority list for an upgrade to Upper but I understand I won't know if I can get this upgrade until I get to the gate.
Am I right in thinking that as long as Upper is not fully booked, I should have a good chance of getting in?
I know this route is busy, but is it likely Upper will be full on a mid-week departure?
Thanks for any tips or advice!
I'm booked on VS019 in Premium Economy for a flight in mid-June. A friend of mine who works with Virgin has got me on the priority list for an upgrade to Upper but I understand I won't know if I can get this upgrade until I get to the gate.
Am I right in thinking that as long as Upper is not fully booked, I should have a good chance of getting in?
I know this route is busy, but is it likely Upper will be full on a mid-week departure?
Thanks for any tips or advice!