They should just close them all, they have the snazzy & rock-solid new banking system now that they aren’t required.
They are paragons of modernity, indeed!
On a more serious note:
I suspect a lot of this is, quietly, intended to drive away their more elderly apathetic customers who like branch banking but don’t make them any money. I say apathetic because they are probably mostly people inherited from the Lloyds TSB split who still use TSB because they have a local branch and it’s what they’ve always done (even back when it was Lloyds TSB).
It is probably the right decision, as it will save them money which they can reinvest in their digital offering to catch up with other players and be more competitive, but you do get to a certain point where having a “branch network” becomes a bit useless because national coverage is so low. Co-op Bank is already at this point, I’d argue, but that’s probably got more to do with their long term goal to merge with another bank than anything else. It’s difficult to run a “branch-banking” brand without decent branch coverage, and they are taking a big short term risk as it will lead to loss of customers to rivals with bigger networks. They may not be the “right customers” anyway, but it will take a lot of work to start winning new customers as their current offerings are not great.
A huge number of TSBs have closed near to me, so by the middle of next year the nearest 3 or 4 from 2019 will all have gone. I don’t personally use branches anyway, but they will need to massively overhaul their processes if they want to be ready for “digital-first” interaction as I’ve found them to be a very branch-oriented bank in the past.