Just an update regarding the problem I was having with the steering being a bit vague due to play on the swinging arm. I have discovered both swinging arm pivot pin bolts needed re-tightening. Once I spannered them there's hardly any discernible play on the swinging arm now and will restore the good handling and road-holding there once was - when the ice has disappeared off the roads, that is! So, lesson learned, check all fasteners from time to time (I usually do, but overlooked these bolts!)
I've been the proud owner of a 1965 BSA Bantam D7 since 1991, affectionately known as Little Willie (Wilhelmina) and love to take her out for a ride so that others can see her.