ex-matelot, indeed the radio check you refer to was the formation leader requesting a formation check-in post-target to discover whether everyone made it through the target unscathed. Whilst NVGs were in theatre and available, they weren't fitted to the helmets nor were the cockpits fitted with NVG-compatible lighting so you couldn't afford to pick them up to see whether you formation members were there or not.
Vendee...I don't know what you were flying but you didn't have to climb to release the JP233. Most ac ran in with Auto-TFR selected, that's the autopilot using the Terrain Following Radar to climb over obstacles on the ground (I know you'll know this, it's for others that maybe don't). Minimum height for the autopilot was 200ft above ground level. But you could disconnect the autopilot and fly the ac manually following the autopilot director cues in the head-up display. That would allow you to drop below the 200ft by up to 30% before the director gave up the ghost. Or you could remove the director cues and fly purely on the radar scope (e-scope)....a lot harder to do but then you didn't get the nuisance warnings. Neither of these options was easy to fly accurately so it could just be that they climbed whilst dispensing.
Luckily, most JP233 targets had fairly flat run-ins to them, (they were airfields after all) so it was relatively easy to drop down running in. However, the JP233 had a minimum height from which to dispense the munitions to allow them to arm and we planned to fly at a height where dudding started to occur, which was below 200ft. So you didn't have to climb to release them. Pedantic, I know but we should strive to be accurate.
The reason the Nav says let's get back down could also be that they left the autopilot connected and the GR1 had a nasty habit of dumping the autopilot as the JP233 cannisters released from the ac following sub-munition dispensing, forcing the ac into a pre-programmed climb.
I'd like to point out that I did not drop any JP233s during Op GRANBY, but I did spend 4-months prior to it planning & flying with them in Saudi & Oman in daytime & nighttime.