From my knowledge of working at IOMPost for a few years several years ago, the yodel parcel contract was lost to manx independent carriers in about 2018 but then sub contracted back because they could not handle the extra. They paid post office peanuts in comparison.
i think something similar happened with hermes and dpd years before that…
if royal mail goes to manx independent, I can see the hermes couriers taking over some of that work, and just having smaller areas to cover with more parcels per street.
it also gives manx independent the option to cherry pick where they want to deliver. For example, they may choose to deliver the royal mail parcels within douglas and onchan themselves but leave all the rural parcels which are not profitable to iom post.
One things for sure, IOM Post are in dire straights. Glad I got out when I could.