Questions are what we are all here for, Sean (well - most of us - the others just want to grouse about what compensation they deserve for the latest slight from US, but I digress).

You will definitely enjoy Envoy to London if you can get upgraded. Those who always fly first may be jaded, but for the rest of us it is great. I have flown four trips to Europe, and got to go Envoy for the first time in January. The best part to me was the room and the seat comfort - you arrive so much more relaxed. The food and entertainment are decent - the former definitely a cut above coach - and the flight attendants attentive (at least on my flight).

Alas, your upgrade won't do you much good at customs. First you will go through passport control. There are separate lines for people with EU passports and non-EU. After they check your passport, you will go to baggage claim, and after you get your bags, you have a choice of exits. If for some reason you are bringing in something you need to declare, you go through that exit where you will be interviewed about your declaration. Most people have nothing to declare and can go out the "Nothing to Declare" exit without stopping. Of course, they have people stationed throughout the area and can stop anyone they choose and take them aside for questioning and inspection.

Good luck with your upgrade and enjoy your trip - London is a fantastic city.

P.S. The Envoy lounge in PHL is very nice - much better than hanging around by the gate.