HelenD
There are ways to include airports as turning points, but you need to forget, momentarily, that they are airports...
As per the FP system, you can nominate a turning point in a variety of ways, for example:
Beacons
Beacon/Radial/DME
Lat/Long
Airways reporting Point
...
So if you wanted to route OVER Cranfield, you don't have to include EGTC in the routing (disallowed) but you could include CFD (the VOR)...
Or, for Blackbushe, you could include this as a flyover point - not with EGLK (disallowed), but as BLK (the NDB) or CPT130017 the beacon/radial/distance location...
Popham - use PEPIS as the turning point in FP and Notam. (Or lat/long or beacon/radial/dme)
The ADvantage of doing this is that the NOTAM will be relevent to your trip height-wise...
The DISadvantage of doing three (or X) different Notam grabs airfield to airfield is that each "flight" has a take-off and landing "phase", so NOTAM outside your selected height band will be displayed.