The loan is guaranteed against Virgin, not you or your parent's house for example, so they will be liable for it, not you. That's one of the benefits of this scheme, they take the hit should it all go belly up.
As the poster above has cautioned, that is not correct. A guarantor provides a joint and several guarantee for a loan should a primary borrower default. It most certainly does not alleviate the primary borrower of liability in the event they default. If the guarantor should go "belly up" then the lender would seek to recover from the primary borrower in the event they defaulted, as well as from any realisable assets from the guarantor. You would not be alleviated in any way by the guarantors inability to pay as the loan would be joint and several. Certainly your parents (unless they were also guarantors) would have no financial interest in the liability for the loan, but you most certainly would.
You should also be aware that even though you may have provided no tangible security for the loan, that wouldn't necessarily prevent the lender from seeking recovery by way of such instruments as "charging orders" if they had unsatisfied court orders and you had realisable assets even if the loan was unsecured, which in this case is unlikely.
That isn't to say this is anything other than a good source of funding for such an expensive endeavour, but go into these things with a properly researched toolkit, rather than advice from the "you are off the hook" merchants. There is always risk attached and that needs to be balanced with a fall back provision commensurate with that risk.