Can I upgrade using Miles for one way only?

[Lydsabug]

We are flying next December and the flights aren't available with Virgin yet (I know its around 11 months out so all good there). My husband my myself have miles enough for an upgrade and I wondered if we could upgrade from Premium economy to UC for just the return flight (or the outbound one if thats easier).

We fly out on 5th December so t would be standard miles but we fly back on 19th December and this is classed as Peak. Any idea how many miles we will need each for either trip... pretty new to the miles system xxThank you xx

[legallyblonde]

I have done this so yes it’s possible. I upgraded my flight from EC to PE outbound using miles and paid for the rest of the family to upgrade as I didn’t have enough miles for all of us