I booked this trip to Heathrow on UA 929 and back the next day on AA 108...just to fly those widebodies. Crazy? maybe

Anyway, i will arrive at LHR Terminal 1 very early (Saturday) and depart again Sunday morning at Terminal 3. I was thinking about booking an airport hotel, but i will probably just sleep somewhere in the airport itself (hey, i've read on http://www.sleepinginairports.net that LHR is not that bad

For those who have been to these terminals before or are familiar with LHR in general, i've got a few questions (I've only travelled through T5 before).
I probably just stay airside, right? So I don't have to clear customs/security...
What are good spotting sites @ T1 and T3?
What's the better terminal, spotting-wise, T1 or T3? Which one gets the nicest birds (T3 I presume) ?
Any recommended sleeping places?
Can I travel between T1 and T3 as much as I like (free or paying)? Or once I go from T1 to T3 I can't go back?
Internet access? Good food/drinks/snacks...?
As you can see it will be a whole new experience...
Thanks in advance!
airtrotter