I have just tried to change my seat on this flight in June via manage my flights; in March both journeys were available. Yesterday and today the outbound says that the seat map is not available and seats will be assigned at check in. The inbound is available. Does this mean they do not know what aircraft type we will be having; so the possibility of an LHR aircraft?
Hi Claire - have a look at this thread and there are others if you try a search.
Best bet is to give VS a call and check with them - even if the flights are not showing on the "manage" section then they will still have your reservation.