Any protection for DL/VS Connections?

Hi All
Looking for some help from those who may have been in a similar position, or even experienced connections between DL & VS themselves.
We're looking at Florida for Xmas and our planned itinerary is below.
Outbound
LHR-JFK then 2 nights in NYC
NYC - TPA/SRQ
Inbound
SRQ/TPA -> BOS -> LHR
We would fund our VS long haul flights in Upper with miles, with DL flights cash purchase. The issue is that Virgin are telling us that if our inbound flight from Florida up to BOS is delayed for any reason, the fact that we have bought tickets with miles & cash constitutes a separate reservation and therefore we would have no protection in the event of any issues or delays which would cause us to miss our VS flight to London that night. However they did caveat that this would be at airport discretion with whatever the agent says on the day.
Clearly this isn't a palatable situation as stumping up for a new ticket just after new year would cost £££.
Does anyone have any experiences of connecting between DL & VS on cash / air miles tickets booked in this way? Have DL helped you get home if there are delays?
Thanks!
Looking for some help from those who may have been in a similar position, or even experienced connections between DL & VS themselves.
We're looking at Florida for Xmas and our planned itinerary is below.
Outbound
LHR-JFK then 2 nights in NYC
NYC - TPA/SRQ
Inbound
SRQ/TPA -> BOS -> LHR
We would fund our VS long haul flights in Upper with miles, with DL flights cash purchase. The issue is that Virgin are telling us that if our inbound flight from Florida up to BOS is delayed for any reason, the fact that we have bought tickets with miles & cash constitutes a separate reservation and therefore we would have no protection in the event of any issues or delays which would cause us to miss our VS flight to London that night. However they did caveat that this would be at airport discretion with whatever the agent says on the day.
Clearly this isn't a palatable situation as stumping up for a new ticket just after new year would cost £££.
Does anyone have any experiences of connecting between DL & VS on cash / air miles tickets booked in this way? Have DL helped you get home if there are delays?
Thanks!