Matthew is a wonderful host, very responsive and flexible. The apartment is in an amazing location on Chiltern near great restaurants and close to the Baker Street tube which has a Chiltern Street exit (note that this exit closes late at night). Bond Street with Selfridges, Mark & Spenser and many shops of Oxford Street, as well as access to Heathrow Street via the Elizabeth line, is also a 12 minute walk. There are also nearby buses; I took one daily to my office at Victoria Station, so tons of transportation.
Check in is managed by a nearby local agency available during work hours who can also store bags for you. The apartment is clean and decently furnished, with a good sized living room. However note that the kitchen and especially the bathroom are really small; my only wish is that the bathroom was a bit larger as I almost got a couple of burns from the towel rack while drying off. If you're a light sleeper, bring earplugs but it's not that loud overall. Great spot!