Preferred London neighborhood (that's not Paddington) for easy access to Paddington Station

Alison - we stayed in South Kensington area last fall and found it convenient because we had easy access to three different lines. That came in handy when at alternate times 2/3 were shut down for a day or two for work. We always had a way to get where we wanted without having to walk too far.
You might want to consider advance construction as you make your pick. Take a look at the planned closures. I'm not sure how closely they keep to this schedule but someone else here might know. We found it very easy to get around London and we often changed lines to get where we wanted to go. You could do the same for Paddington.
tfl

Easy access to Paddington station implies to me somewhere on a direct tube line to Paddington.
Consulting the tube map here: http://content.tfl.gov.uk/standard-tube-map.pdf that would rule out Victoria (need to change), South Kensington is OK (5 stops), Bloomsbury is a bit far.
I would choose anywhere up to 4 stops away on a direct tube line.

Note Paddington tube station is slightly confusing. The Bakerloo line (brown) and District line (green+yellow) are indeed "underground". The Hammersmith & City line (purple+yellow) is on the surface, same level as and part of the main line station and not connected to the other lines.

South Kensington and Victoria are named stops on the Circle line (yellow on maps), which goes to Paddington with a few stops in between. Someone else can help you with Bloomsbury as I am not sure which tube stop would be closest.

As for the Heathrow Express, if you decide on that, buy your tickets now to get the 30-day advance price of £14.40 ( £8.80 if you are fortunate to arrive on a weekend or bank holiday).

https://www.heathrowexpress.com/tickets-deals/prices-fares

If in the Victoria area don't ignore the existence of the 36 bus as an option to Paddington, especially if a stop is nearer than the Underground. This does follow a more direct route than the Circle Line.

The bus is a great idea! We much prefer it to the tube in London.

Please look at the hotels closer to Bayswater Road around Lancaster Gate/Craven Terrace. They are walkable to Paddington yet a little bigger and not as “touristy” as some of the ones right by the station.

To all -
Thanks so much! I truly appreciate your responses.

@Nance What a great point; I hadn't thought about the construction angle. (Why not?! I think about that at home for getting around our area's awful traffic.) I've been haunting the TFL Tube website, but hadn't checked advance construction. Just did; nothing scheduled in "my" areas, but hey, no guarantee there wouldn't be. So, having multiple options sounds great. A + for South Kensington.

@ChrisF Terrific rule of thumb: 4 stops away. Thank you! I'll keep that in mind as I narrow down my homebase choices. Think Bloomsbury is off the list, for access to Paddington and other reasons. Also, appreciate the heads-up about the location of the lines in Paddington tube station. You may have averted some future crazed searching.

@Lola Thanks for the tip about the Heathrow Express! (BTW, to Express or not Express seems to arouse passion among some travelers, based on past conversations I've read.)

@Marco @Emmma Ignore the 36 bus? How about I didn't even think of it?! (Again, what is wrong with me; I take the bus all the time at home.) And, I recall taking buses when we were in London before. Anyway, thank you both. Time for me to dive into that bus schedule.

South Kensington/Gloucester Road/Earls Court are all easy access to Paddington as well as on the Piccadilly line to Heathrow. It's 40 minutes from Heathrow to Earls Court..

Unless you are staying near Paddington, taking the Heathrow Express means you would still need to catch the tube, a bus or a cab to your hotel.

For easy access to London Paddington, we stay by the Lancaster Gate tube. An 8 minute walk to Paddington makes this neighborhood ideal. We've stayed at the Corus Hyde Park Hotel.