Both that one at the end but also the "spiral" one to the right on entry. There was talk that they'd allow direct boarding to the train from the upper level but it would only be to the far right platform and I've never had a train go from that platform!

One thing I find in the ground floor part of the lounge is that there is poor mobile phone and wireless coverage to the point of both being unusable.

There are 4 things to look at when comparing classes of travel:

Standard economy doesn't get any of them.
Leisure Select gets you the 1-2 seating and the meal/drinks
Business Premier gets you everything

If you have a Platinum AMEX you get Lounge access
If you have a Eurostar "Carte Blanche" card you get Priority check in and Lounge Access (card not that difficult to get if you do a few return trips)