When I passed Lympstone Commando in both directions late on Friday night, no one needed to use the station. The station has been updated with lighting. When I went there a few years ago, I quickly jumped the wooden fence, took a photo of the sign then jumped back over.
Norton Fitzwarren - I walked through a small field to get as close as possible to the platform. There was no station sign and it was possible to jump the fence and cross the track but the adjacent works had people milling about so I thought better. Saying that, I was within 10 metres of the halt which was close enough for me.
Worcestershire Parkway - it's almost built and there was a clear sign outside it. I've sailed through it recently on XC with people building the car park. I just parked up off the roundabout and had a little nosy. That's enough for me.