Confused about where to stay in London

South Kensington and Earl's Court are popular, particularly with North American visitors, but personally I fin them a bit too far west for most attractions beyond the museums on Cromwell Road. There are certainly plenty of hotels in Mayfair, Knightsbridge, Chelsea and Belgravia but you aren't going to find much in the way of bargains there. Westminster is in the same category but very central.
In truth anywhere within the Circle tube line (the yellow line on the tube map) or just south of the river in that area is a good location for tourism and looking a bit further east might produce some cheaper options.

Already suggested two options in your previous post. Were they unavailable?

We always stay in the Belgravia area (6 times maybe ?) About three blocks from Victoria Station. Easy to get to from Heathrow and close to Buckingham. The last three times has been the annex of the VS Best Western. Good restaurants, pubs in the area plus a laundry service.

My "go to" London hotel is Premier Inn Waterloo or its neighbor Premier Inn County Hall. Both are an easy walk across the Bridge to Westminster and close to multiple transport options.

I've spent about 300 nights, give or take a few, in Earls Court. The area is fine. When I first visited the area over 30 years ago, it was known as "Kangaroo Court" because of all the Australian hostels. Now it's made up of multimillion pound apartments and townhouses. Some have been turned into smaller hotels rented out like AirBNB's.

Take at look at the Premier Inn Earls Court for reasonable priced rooms.

South Kensington and Gloucester Road areas are good. Mayfair, Knightsbridge, Chelsea and Belgravia are some of the most expensive areas in London. No budget hotels.

What is your budget?

I like booking.com to do research and sometimes book through them as well.

Mid June is going to be expensive .

A lot of members on this site are fans of Premier Inn's.

I have stayed twice now--10 years apart, second time last April--at The Baileys Hotel in South Kensington, just across the street from the Gloucester Rd tube station (several useful lines there) with pubs and other restaurants nearby. 10 minute walk to the V&A, a bit further to Harrod's. It's a lovely hotel, rooms are large and clean and the service is excellent--I looked at other places in the area but it's now the place I prefer to stay.

Rembrandt Hotel near the South Ken tube station and easy access to several bus lines.

Yes Mayfair is a very nice area, full of money, and no you can't find a reasonable hotel there.

Rick has a lot of suggestions, did you not find anything interesting? He seems to focus on Knightsbridge near Harrods.

I've stayed in Earl's Court area before and it's fine, but I found the tradeoff of lower price for more travel time to be too much. I'd rather pay a little more and stay closer to all the attractions I came to London to see in the first place. I like South Kensington area, and we've stayed in that area on two separate trips. We've also stayed close to St. Pancras/King's Cross and in the Belgravia neighborhood on other trips, but I like those areas a lot less than S Ken.

Everyone is going to have their preferred areas of London, and there's no one "right" answer. London is a big city and the main sights are spread out, so no matter where you stay, you'll still have to get on public transit at some point. I wouldn't stress overmuch about
getting the perfect neighborhood or the perfect hotel. In general, hotels in London are just expensive - it is what it is. If having a nice hotel is important to you, it might be worth stretching your budget to stay closer, rather than trying to save money by staying further outside the city.