I don't think they all result in AAIB reports. A Yak was flown 'throgh' some trees at barton on approach a few years ago severly damaging the aeroplane - if it had been anything less brick-built it would have been a fatal. No AAIB report. The Yak was not UK reg, but other non-UK Yak accidents have been reported.
And the aeroplane that crashed near Lambourne, on the downs north of Membury, a couple of years back in apparantly good weather - yet some sort of in-flight break-up - again no AAIB report.
SSD