I can't remember the last time we went into the town centre, for all the reasons you mention Nigel and add the chuggers in as well. Closest we get is the Lidl store on Saturday morning.
There's just nothing special about the High Street for us. Those like Mary Portas who are trying to revive the old traditional version of the town centre are on a hiding to nothing IMHO.
As for the next store chain in trouble, I'd look at the department store model: Trying to be eveything to everybody often ends up being nothing special for anybody.