1.5 dci intermittant starting when hot.

Hi hope someone can help. had a problem with my micra for several years now and its driving me up the wall. the enginge normaly starts ok but if i do several short trips at some point when it try to restart it will initialy turn over ok for a short time but not start . on trying again it will give all the symptoms of trying to start with a low battery. ie turning over slower and slower then not tuning over at all. if i wait 20 min to 1/2 hour it starts like nothing was ever wrong. and then carrys on starting.

info . 160,000 mls on clock
injectors changed
fuel fiter changed , several times now
injector return lines changed
glow plugs changed
glowplug relay changed
battery changed and second one checked by halfords
batt connections checked
fault codes read by injection specialists nothing serious found even when i offered money
fuel pressures checked
Fuel filler cap checked
water pump changed
timming belt changed
fan belt changed
alternator changed
radiator changed
cam and crank , temp sensors changed
valve that i cant remember the name of that lets coolent flow when engine up to temp changed (Sorry dyslexic memory fail)
starter motor start voltage checked.
you can see occasinal bubbles in the fuel lines but no more than when car was starting ok, also tryed pumping plastic bulb wth no change to bubbles

Help would be appreciated thanks