The documentary deeds are of little importance anyway. (The deeds to my house are in a drawer right next to where I'm sitting. If I was to look in that drawer and discover that a mouse had nibbled his way through them I would be completely unconcerned).
What really matters nowadays is that the Land Registry's electronic records are correct. (They take precedence over anything you might have on paper). Once the mortgage is paid off, it would be worth investing £4 to check that the title register for your property is up to date:
https://www.landregis...ortal/Property_Search
(When I sold a small part of my garden to a neighbour I discovered that the Woolwich had forgotten to advise the Land Registry that there was no longer a charge against the property, even though I'd paid the mortgage off 15 years earlier!).
There is no point whatsoever in storing your deeds with your bank. It's just a (so-called) service which they offer to get money from you.
Chris