If its more than 3 hours change, then you can likely change under (ii); though quite how Virgin interpret "next" as opposed to closest may cloud things.
I think these are the current Ts&Cs:

21.2 If we change our schedule before you fly

(a) If, after issuing your Ticket, we change the scheduled departure time, we will notify you if you have given us or our Authorised Agents your contact information. You should check our website before you fly for the most up-to-date flight information.

(b) If the new scheduled departure time is more than three (3) hours after the previous departure time or less than three (3) hours after the previous departure time but you provide proof (upon request) that the change will cause you to miss a connecting flight or cruise and you had allowed the minimum time to make the connection prescribed by the relevant airport or cruise provider, you will be given the choice between:

i) a refund of the unused portion of your Ticket;

ii) travelling on our next available scheduled flight (subject to availability of seats in the same class of service for which you originally purchased your Ticket); or

iii) travelling at a later date. There may be additional charges to pay if there is a difference in fare, carrier imposed charges and surcharges, taxes, fees and charges. These will be advised to you at the time of rebooking.