A
Travelcard would be valid in the way you describe, however Virgin have their own product which they
call a
Travelcard but they claim is a different product, which is is the same as a Travelcard
except the
outward journey is valid by the "booked train only" ie, considered to be an Advance single for that leg!
According to the definitive source of information for all Train Companies,
NRE:
"Ticket terms and conditions are now the same across all train companies nationwide, so you know exactly where you stand."
" The new names describe when you can buy or use a ticket making, it easier for you to buy the best value ticket for your journey"
It is unclear, therefore, whether Virgin's different T&Cs apply or not. You may want to consult your solicitor before making a decision...!