I'd say your GP was wrong in the fact he was concerned bubs heart was having decelerations but definately right to sent you to the hospital for a CTG if he was concerned which obviously he was. You can't be to careful with these things.

The reason I say this is because bub was moving around at the time he was using the doppler which would make its heart rate accelerate not decelerate. I'd say he/she was having an active period making it hard to get an accurate sound of bub heartbeating because of the movements. Perhaps he was picking up a combination of both yours and bubs or bubs heart rate was actually alot high then its normal resting heart rate and when it did stop moving and its heartbeat returned to its normal level it gave the impression it was decelerating when in actual fact it was probably going fast then returning to baseline if that makes sense. The fact bub sounded/looked good on CTG and fetal movements sound good would give me reasurance things are going along smoothly despite the scare this morning. I too would just keep an eye/feel for your baby movements and if they reduce head back up for another CTG or scan to check placental flows. The first sign of a compromised baby is lack or reduction of his/her movements.