I phoned the unhelpful helpline this morning, rather than wait 5 days I contacted my bank who weren't the least interested. The bank adviser reassured me that the worst that could happen is that a direct debit could be set up without me knowing!
Oh that's just great, I told him to make a note on my computer records that I had given the bank the heads up. I am now waiting for the letter to arrive from Innsworth. By the way, Innsworth will be using stored addresses for retired personnel, so if you have moved you stand a double chance of details going awry!