Shy,
It was always drummed in to me when training on the 135 and on subsequent checks that, if the Red Low Fuel Lights came on, regardless of what the gauges read, assume the Red caption is telling the truth and land.
Interesting that Bond have decided to up the MLA to 90Kgs - so, now you have a situation where you never get to use the fuel in the supply tanks and never get to see the levels reducing so you never know whether the gauge is reading correctly or simply "stuck".
Beginning to sound to me as though the 500/1000 service ought to include a fuel system drain and re-fill to check the gauge accuracy.