Thanks for the run-down. It's always useful to know what to expect and be as prepaired as possible although from the many accounts you read on here it seems eveyone's mileage varies. I have my initial class one booked three weeks from now, so it's good to hear that things are pretty much as I expected.
I'll just add one thing though - when I booked (at the end of Feb for a mid Apr booking) I was given the choice of three times: 8:30, 9:30 or 12:30. This came as a surprise since what I had read on here suggested it was either of 8:30 or 12:30 to choose from. I thought I would share this as it may be of use to anyone planning "in and out in a day by air" visits to LGW.