On arrival in London, immediately check the monitors for your onward flight before heading down to the train. Being an A380 I believe means you will always park at the C gates, so if the flight to AMS is going from B or C you can avoid a trip back to the main terminal AND take advantage of the ultra quiet (well it always looks like that to me) mid-field security checkpoints.

There's a lounge in the B satellite and both have F&B offerings. Again, way less crowded than the main terminal.