A displaced threshold is simply based on the OCH's for the approach to the runway concerned. If you land before it you have technically landed short of the runway. The papis (if available) are calibrated to give the glideslope to threshold gradient , usually 3 degrees. So if you land short you have cocked it up good style. If you do so, reporting action is mandatory from ATC.
But in reality most ATC'ers couldn't be arsed filling out the paperwork so we'd grass you up to your flying club and probably dispense a high minded bollocking over the phone
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No, you can't have 09!