I can only suggest you fly into one of the more popular gatherings in the upcoming summer, and google your reg. in the subsequent weeks. Myself had the best success (if success you will call it) at Schaffen EBDT mid-August, the place is literally crowded with spotters and some are generous in sharing their photography.
Jan has it spot on. I occasionally Google my reg and see what other photographers or plane enthusiasts (trying to avoid the word "spotters") have uploaded. I once flew into the Little Gransden airshow a few years back and there were more photographers lined up at the runway threshold than photographers at a red carpet waiting for someone to pounce on Brad Pitts groin.