I was surprised by several parachutists opening their 'chutes around me when I was flying North over Lancaster/Lancaster University earlier this year (took some photos).
They were about my level (circa 3,000 feet QNH) and probably operating out of Cockerham. The wind was easterly, so upwind would have been in the Lancaster/Thurnham area.
That was the only time in all my years of flying that I have encountered anything like that - suddenly in my vicinity, but obviously unseen until they opened their parachutes.
They were some way away (maybe a few hundred metres), so no immediate danger of a conflict.