Originally Posted by Often1

First, if you don't like the tentative rebooking, call VS and ask for the rebooking you wish. It ought to be easy enough to be rebooked onto a DL service to LHR.

Second, the "duty of care" has nothing to do with this. Rather VS has a duty to get you to LHR. Thus, you should have ask for a bus voucher or at least a reimbursement of the bus ticket afterwards. You could also negotiate for a simple payment which gets you to where you are going. But, anything over the cost of the ticket to LHR is a simple customer service gesture.

Third, you may also be entitled to cancellation compensation under EC 261/2004, all depending on the original timing, the new timing and the actual time of arrival at LGW/LHR depending on where things wind up.

The key to these situations is to be proactive. If what you are offered isn't to your liking, do the research to find what is and call in.