Firstly can I reasonably suppose that a pitot tube sensor will give me all the data I need ignoring variations in temperature and QNH?
Lincoln, what you'll get with that setup is indicated airspeed only. True airspeed in flight can be determined after recording temperature and air pressure. TAS formula is indicated airspeed times square root of air temperature at flight altitude plus K (459.4 for F and 273 for C.) divided by ISA temp. (59F or 15C) plus K times ISA pressure (29.92) divided by the air pressure at flight altitude. In general you can assume TAS by adding 1.4% for every 1000ft of altitude. In modern aircraft the inputs are digitized by the CDU. Hope this helps.