.. Shipton under Wychwood, a roe deer ...
I'd had a similar encounter, but at a more comfortable 10m distance, around Basingstoke, riding S. last Monday.
Are roe deer common in those areas?
Yes. They're common over the whole region. When commuting by train from Reading to Basingstoke, Newbury, & Oxford, at various times, I saw them very frequently, sometimes multiple sightings in one trip.
I've often seen them when out on the bike, sometimes crossing the road, & I once had a near miss as close as yours, when one roe deer leapt across the road in front of Adrian Lawson, & another between Adrian & me, near Beenham (a bit west of Reading). Luckily, my bowels were already empty.
Several witnesses to that near miss. It was a Reading CTC Wednesday evening ride, a few years ago.