Lemain
The pilot flew from North Weald to Shoreham and maintained his assigned course and altitude without any significant deviation as recorded by ground radar.
Calculations generated from ground footage of the display and cockpit video footage where the airspeed was visible are in close agreement.
The pipework connecting the instruments to the pitot tube was too damaged in the crash to be able to test it, but even after the crash, the somewhat damaged instruments still performed almost to specification.
Every indication is that the instruments were working correctly and any errors displayed, such as the left hand altimeter lagging and under reading slightly, would act as a cue to the pilot to fly higher and faster, if anything.
You are grasping at straws pursuing this as a possible reason for the accident.
What may be of relevance and something that was glossed over in the report is that a GPS device was fitted in the cockpit. Is it possible that this was being used as a quick source of positional reference by the pilot rather than doing a proper cockpit scan? Now that would make sense if the GPS was being used to assess ground speed. The difference between miles per hour and knots would account for the low entry speed into the bent loop manoeuvre. I believe the GPS display was mounted higher on the instrument panel and would have been more immediately visible glancing back and forth between outside and inside the cockpit. Shouldn't be used as a reference, we all know that from the sorry tales of pilots attempting unapproved GPS letdowns in bad weather, but the temptation is there.
I believe that this is a far more likely scenario than faulty airspeed and altitude indicators with a pitot problem, when every test that could be conducted suggests that they were working normally.