I appreciate that there are probably not many status or business passengers from GLA but as a GGL(FB Ultimate) refugee I thought I'd contribute.
When I flew in September 24 GLA to AMS they used the Upper Deck lounge which is tolerable but really nothing special. I've been in Eastern European contract lounges which are better.
They have at some recent point shifted to the Lomond Lounge which has always tried to set itself apart with quite a high fee and is a paid for lounge with Premium Pass.
I admit to never trying it as I'm too cheap to pay for lounge access, though last night I did consider the uplift to try it as I don't like the Upper Deck especially it's chit system for only two alcoholic beverages.
The Lomond lounge is a world apart. Great seating. Great airport views. Great service. I was automatically on a list they don't even scan BPs. Pretty good breakfast selection. Great service at the bar with properly made drinks. I'm having a lovely Bloody Mary.

Only slight downside it is further from the usual gate for KLM. Allow 10 mins.

Here are a few photos