There are 2 boutique hotels I have stayed in 2 times each--I tried to branch out on my trip last April and realized I had 2 favorites, why mess with that?!
Hotel Caesar on Queen's Gardens, 10 minute walk from Paddington, 10 minute walk to Queensway with 2 tube stations and numerous shops & restaurants. Quiet residential street with a garden in the center so it's peaceful. Hotel is nicely appointed, friendly staff, rooms are modern and size dictates the cost. Included breakfast was good & sufficient.
My top favorite, however, is Bailey's Hotel, just across from the Gloucester Rd tube station in South Kensington, which is a wonderful area for museums & restaurants. I stayed there again last April and had a deluxe room--first trip after covid restrictions called for a splurge--and it was enormous & very traditional/classic in it's decor. The hotel itself is very stylish and well-maintained, very pleasant staff. I did not have breakfast there, but it's offered.