Thank you all. Making me feel better. I was posting on another board. Many people on that board were saying we would not make our flight (but I'm not sure how many of those posters have actual experience with this transfer) and I was getting into a panic. We got a great fare but nonrefundable tickets.

Yes, we are flying Maxjet to IAD, leaving 1PM. It's their new service starting March 15th. I am a little worried about the flight into LHR. I have had to circle a bit in the AM. I'm just hoping that traffic on Sunday AM is a little lighter (it's off-season and non-bank holiday).

Looked into easyjet but their flight also does not get us into the airport in time.