But he got 600 per person already - so as other say unless he's paid more than that for the 14th night, how can the OP claim to be out of pocket overall?? You can't claim for something that you aren't owed regardless of who has already paid/compensated you.
I'm aware he's got 600 compensation, I'm not sure he is claiming to be out of pocket overall.
You go to court when you are "out of pocket" or when you are owed a debt.....you can't really expect to claim in court when you are already in "profit"
but that is the thing, is the 600 not for the flight?
you'd be getting that whether you were staying in a 20 a night Airbnb room or a 2000 a night suite - of course in those cases, if booked individually then it isn't down to the hotel or airbnb owner to compensate you (you'd perhaps have to chase your insurance provider for compensation), in this case though he's booked a complete package with Virgin... I don't see it is unreasonable for them to put him up for the number of nights he paid them for.
maybe there isn't anything he can do, perhaps legally speaking 600 is all he's entitled to, I'm just objecting to the idea that he should be happy because he's got something or is "in profit", it isn't unreasonable in this case for him to ask that they cover the cost of the additional day required to give him the 14 day holiday already paid for.
IMHO if they cover the cost of the full 14 days he originally booked rather than him now having to pay extra for the 14th day then he's still owed the 600 for the flight - that is compensation paid for the inconvenience of wasting a day of his life with a delayed flight irrespective of whatever else has been affected AFAIK.