Don't you know about the Moutai lounge where you can drink as you please?
When I was in London, the weather was nice. It takes about forty minutes to get from Park Lane Intercontinental to Heathrow T2 by taxi without traffic. The taxi queue outside the hotel to T2 costs 72 pounds, plus a 5-pound terminal drop off fee for a total of 77 pounds.
The CA856 flight at 17:40 London time from Heathrow T2 was not crowded that evening, and it took a total of ten minutes for check-in and security. Air China is always in Zone B, so head that way after security and shopping. In Zone B, there are United Airlines, Air Canada, and Singapore Airlines lounges, but the Singapore Airlines lounge is under renovation and is expected to take another four months.
The 5-pound drop off fee at Heathrow T2 is mandatory and will be collected with the taxi fare. It costs 77 pounds from Park Lane, and there was one time I took a taxi from T2 to Westminster for 120 pounds. There were four or five counters open at the Air China desk at T2, and after checking in and security, I headed straight for the Zone B lounge.
I wanted to go to the Singapore Airlines lounge, but it was under renovation, so I went to the Air Canada lounge across from it. The Air Canada lounge was not too crowded, the hot meal was tomato meatballs with rice which was decent, and there was a self-service Moutai bar. Outside the lounge's floor-to-ceiling windows was a busy scene of 'planes coming and going'.