Well, for good or ill I have made a decision and taken the plunge. I have had quite a few suggestions both from here and elsewhere and have ended up with - and why do they have such a wide set of shorthand designators!!
Sony 16-50mm f/3.5-4.5 ZA VS T* DT second hand but absolutely immaculate. I ended up with this one as it was the lightest of all the ones I considered and as it will often be my walkabout lens I felt that was important too, especially at my age!
Tamron SP AF 70-200mm f/2.8 Di LD (IF) macro, brand new. I realise that this is at the opposite end of the weight spectrum but will probably always use it on a tripod.
I did not go for a 300mm as, when I looked back, I didn't use that length much.