Heliport the only fuel figure that should ever be written down anywhere is total fuel on board...as Tarten says it's the PIC's responsibility to know what proportion is deemed unusable.
GK430
I can only assume that because the taxi fuel is such a small amount in most 2 or 4 seat trainers a level of complacency comes into play.
My aircraft, an IO550 powered A36, has a EDM700 with fuel flow transducer/computer giving extremely accurate readings (+/- < 1lt) and I use on average about 2 liters from start to airborne. And yes I make allowance for that in fuel calcs.
While fuel gauges on light aircraft in general aren't great I find if I compare fuel gage readings AS CORRECTED BY THE FUEL CALIBRATION CARD and compare that to fuel remaining via the computer I can get pretty good results. Mind you my aircraft would be refuelled to full tanks on average every second or third flight thereby resetting the fuel computer to the programmed full tanks fuel total of 280 liters. A Baron I fly occasionally does not have the fuel computer but comparing corrected fuel gage readings to estimated FOB using realistic FFs and slightly buffering required reserves keeps that safe.
Chuck.
PS so your CAA are very much like our CASA...Cretins Against Sensible Avation.