Used the fast lane and GVK lounge yesterday prior to the BA198 (daytime BOM-LHR). Observations:
1. Fast track very quiet, no preceding passengers at either security or immigration.
2. There was a dedicated immigration agent serving Business/First (although no First on yesterday's 198).
3. Although fast track very quiet, I saw the immigration officer turn away non fast track passengers; sending them back to the very long non fast track queue.
4. Immigration was the first point at which I was asked to show the boarding card; I could have passed through fast track security with non fast track status.
5. The GVK lounge was a surprise after being accustomed to BA galleries lounges; quiet, clean, fresh, attentive staff and Moet willingly offered.
6. On leaving GVK for the gate, outside the lounge a BA employee advised that although shown as only 15 mins late on the screen the actual delay would be longer and she recommended us returning to the lounge and she would come and get us (and other passengers) when boarding commenced - which she did.
7. Other GVK user appeared to be a small number of Jet Airlines passengers for middle eastern services and a few for Jet's LHR service, timed to leave 5 mins after the 198.
8. Overall, passing through BOM/GVK was a very pleasant and stress free experience.