Taking advantage of the last few weeks of nice weather, we visited Harcourt Aboretum on the last Sunday of October and then Warburg Nature Reserve on the first Sunday of November.
Harcourt Aboretum is just south of Oxford, about a ten minute drive from us. It's part of the Oxford Botanic Gardens, which are part of the university, so entry is free to university staff. The day was overcast and pretty windy, but when well rugged up it wasn't too bad - and we had Helen snuggled up in the Baby Bjorn carrier - and we caught the maples in fine colour. We came back via Marsh Baldon, where we had an early dinner in the Seven Stars pub. (Note for parents: the loop we did would have been strollerable.)
Warburg Nature Reserve is one of the "flagship" reserves of the Berks, Bucks & Oxon Wildlife Trust, about 40 minutes drive southeast of Oxford - at least if you don't have navigational problems as we did - not far from Henley-on-Thames. We did a short 1 mile "wildlife loop", this time with Helen in the baby backpack (if it hadn't been raining a stroller would have been ok). We came back via the B480 (which becomes Cowley Rd) and would have stopped for afternoon tea in one of the little village pubs if Helen hadn't fallen asleep in the car.