Cotswold Eagle

I understand your wishes, but do keep in mind that London is one of the most expensive cities in the world to stay in. If you think you have found a real bargain, almost certainly you haven’t, and one of your criteria will have been badly compromised. Plenty of threads on here with recommendations that do fit your wish list, and if you see a decent rate at one of those, don’t hesitate, particularly if it’s one you can cancel.

Yes, it’s upstairs at that end of the station. There are lifts, which will be easiest with the luggage. Well signposted, including a floor trail, as with the tube lines at Paddington.

The added danger of people using this phrase is that there is in fact an area of London called Downtown - it’s in Rotherhithe (south east London), by the river. Definitely not where people probably mean and not a tourist area!

Oh, my. I assume you must mean Green Park, the route already posted by Globaliser. As a user of the bottom end of the Jubilee, ‘ never change at Green Park’ is a personal rule, but if you must, follow G’s first suggestion, the ‘Way Out’ route… Well, it’s a darn sight closer than LHR 🤣 My preferred route would actually be train to Paddington, then Bakerloo and Jubilee lines, using the easy level change at Baker Street. I accept the added expense to avoid the interminable Piccadilly leg to Heathrow (which I have done dozens of times), but I am in a minority on this board! Doesn’t matter to the OP, of course, given the rail strike.

As I understand it, a different operating licence is required for vehicles taking more than 9 passengers, so the services you are looking at probably offer cars or MPVs seating up to 9. You need to be looking for coach and minibus (what in the States would be called vans) operators. I don’t have any recommendations I can make, but they exist and hopefully our resident ex-professional drivers or others will be along shortly!

Yes, it does, so no chance for the OP to miss swiping in or out.

The real bottleneck recently has been ground handling, particularly delivery of baggage (but also getting aircraft onto stands) caused my significant staff shortages post-pandemic. BA has been badly affected at busy times. I've not been through LHR for a few weeks, but my impression is that is getting better for arriving flights. Hopefully some of our more frequent flyers will chip in. I think you can change National Express tickets to later services if delayed (only at the airport), but John B will hopefully be along to confirm that.