Thanks for all the research Lastlid.
Hopefully the info' you've dug up will be of some use to the OP.
In a sense they need to 'stand it on its head' as it were, because they'll be wanting to prove the OP's partner WAS resident in the UK for more than a certain length of time each year (91 days),rather than absent... as you'd want to show for tax (avoidance) purposes.