The view now is to keep your deeds and I give the owners the house's deeds to the buyer in personam as they say.
I assure them if they send them into the Registry "just to be sure" they will shred them
Mortgage charges MAY be registered, some are, some arent. As above no record does NOT mean the property isnt mortgaged (*)
there are things called over-reaching title - which have effect even if not recorded and these are mainly Mining rights
and yup up my end of Oldham Rd His grace the bishop of Manchester reminded us he had an over-arching right to mine under my prop in Newton Heath - it cd be over-reaching I cant remember
see here: it is the kind of thing they inflict on land law students
https://www.chba.org.uk/for-members/library/overseas-seminars/qualified-indefeasibility-of-registered-title
Land registry fraud is a different subject