Please settle my mind (Heathrow to Stansted).
 

We will fly in to Heathrow, arriving at 10:20am. I have made a reservation with Just Airports to get to Stansted for a 7:15 flight. I think this should be plenty of time. Sound right?

Also, assuming everything goes as planned, we could have several hours at Stansted. Any suggestions of things to do in the airport or nearby (is there anything near by?)?

This should be plenty of time, barring the worst of disasters. From my recent experience any flight in/out of Heathrow is likely to be delayed considerably, but even so, you should be fine.

I think if you can manage the luggage I would go into central London for a couple hours, which would probably negate the usefulness of using the Just Airports service.

Making the connection will be no problem. However, you might consider just going into London for the day. You'd have at least 3 or 4 hours to spend in the city. Depending on how much luggage you have, you might even have time to come in by Tube (otherwise, Heathrow Express is a very fast way to Paddington Station). Stansted Express leaves from Liverpool Street Station, however, and that's pretty inconvenient. I'm just saying this because there's not much to occupy you at Stansted Airport for several hours, so it depends on how much you want to see just a bit of London.

In the (admittedly unlikely) event of evrything running to plan, you'll be at Stansted just after 1, with nothing to do. It's got the weakest retail therapy of any London airport.

You might explore buses into Cambridge (at www.nationalexpress.com)or Colchester, which is an undervisited dull town with a surprising amount of Roman remains (http://www.firstgroup.com/ukbus/sout...nkwebmar04.pdf). You should have time for at least a gawp at King's Parade.

The nearer Saffron Waldon has shorter, more frequent bus journeys. Nothing like as interesting as its name, but pleasant to mooch in for an hour or two.

Great Dunmow has even more frequent buses. Little to look at, but Google on its flitch and see whether you'd like to come back in 2008.

There is a left luggage facility at Liverpool St
http://www.excess-baggage.com/contact.asp#Liverpool

So you could explore a bit of London from there, having been able to check timings for the onward journey to Stansted - if it's a Sunday, the Spitalfields market/ Brick Lane area is on your doorstep, or you could get a number 11 bus for a drive through the City to Trafalgar Square and Westminster (depending on how much time you think you have)

http://www.tfl.gov.uk/tfl/pdfdocs/tourist.pdf

Thanks for the great ideas. We will be returning to London at the end of our trip to do some sight seeing.

I think getting to Stansted, checking time, then heading out from there would make me feel better. Is there a place to leave luggage there?

Not that I'm really an expert, but sometimes (usually?) flights won't let you check in until it's three (?) hours before scheduled departure -- or whatever the number is. So if you make it to Stansted and leave your bags there and then leave again, you may not accomplish much anyway. It may just be better to think about where you can leave your luggage at a place that's convenient for you in terms of exploring London and return to Stansted.