Not exactly intercepted, but once on my way to Westbury, over the White Horse, in a K18 glider on a 300 k attempt from Booker, getting uncomfortably low, I didn't want to leave the thermal before getting to cloudbase....
Boscombe Down? down there someplace.....peering at my map...
When a couple of military aircraft, one above and one below, sandwiched my glider.
It don't half get your attention. I think they must have been playing games, but I did promptly skedaddle back out of their territory....