Having removed my sump on a classic i found that i couldn't remove it from the car because of the dipstick tube is jammed into the sump and the tube will not come free of the car because it does not fit behind the cam cover because of some pipe work. I have tried pulling and twisting it to no avail and pushing and twisting. Is there a correct procedure for this job?
I have soaked it throughly in wd40.

 

Plenty of WD40 as you have done and pull upwards while twisting
side to side - they do tend to corrode in place .
If you break it trying to get it out,give David @ API a ring and get a
replacement one