I have read through the stuff I have and nowhere does it say it triggers a redemption, to be honest I know this without having to read them

It mentions continuing on with the facility account even when the mortgage is actually paid off, initially you would have had to close the facility too when the mortgage was gone.
I have not paid interest on my mortgage for over 10 yrs, yes for some of those years I might have been able to get a better rate investing the money and I did that with some of it but I have left enough to cover the full amount (which is small at this stage) between the facility account and the other offset accounts.
You definitely were never meant to have an offset mtg on a rented property, it refers quite explicitly to that and says you can be removed from the product if the house is let. It is meant for your principal private residence only. Nowhere on my loan offer does it refer to it as a 'residential investment loan' but having said that it is true that UB in general haven't a clue about this product bar a few staff in Head Office who used to know, in fact one used to post here I'm pretty sure!
UB would happily get rid of all Offset mtgs if they could I am sure and unfortunately a lot of customers don't remember some of the great features and benefits of this product either and don't use it correctly.
You did well cremeegg getting money out of them if you now have the property rented as it's crystal clear in the documentation that it is for PPR only, although maybe it was for other shortcomings in their dealings with the account