I get Carte Blanche through my company as part of their corporate deal. It is possible to credit trips to your personal account and then use the CB as a way to get fast track security, lounge access and jump the taxi queue (all 3 very useful at Waterloo IMHO).

On the meal front, both Leisure Select and Business Premier offer meals of some description throughout the day. The best deal is in the evenings (departures after 5pm) when a full dinner is on offer, but even mid-afternoon you'll get a 3 course lunch/snack, with wine and a bar service.