Just completed a two night stay here. Got a great rate via price match, paying just £92 for the two nights.
Had an email query which went unanswered for a week but rang up a few days before and got the info I wanted.
Booked a single room (seldom see those in the UK, at least in chain hotels?) and got exactly what I paid for so no upgrade. To be fair, judging by the app all the rooms other than singles were sold out on my 2nd night so they were genuinely busy. I certainly didn't press the issue anyway. Was thanked for my loyalty and got two breakfast vouchers for the on-site 3rd party restaurant. No drinks vouchers, not sure if that is a thing here or not.
Check in was a bit slow due to their systems "updating" and this required the poor agent to jump from one desk to another and finally admitting defeat and asking me to come back later to pre-authorise my card. I had a letter under my door the next day reminding me to come by again before checkout. Not exactly sure how the Hilton payment systems work but I'm sure they've taken payment just off my stored card before.
Anyways like I previously said there was no upgrade so had my pokey little single room; the bed in which seemed more like a small double which was good. The room was fairly modern albeit small but perfectly adequate for one person, the bathroom even smaller! Shower was powerful enough to strip paint from the wall, very powerful and as a result flooded the bathroom and the step down into the room. Lesson learnt for proceeding showers. There were tea and coffee making facilities in the room and water in the fridge.
After I got to my room the front desk agent rang to ask if everything was okay with the room and to ask me if I needed housekeeping. I said yes, and the next day a full service was done.. They didn't just chuck fresh towels on the bed!
As previously mentioned breakfast is served in the on-site restaurant and is provided by the restaurant /cafe sharing the building which AFAIK is not affiliated with the hotel other than being their breakfast "contractor". They have a room set aside for hotel guests although when it was busy they were seating hotel guests in the main restaurant. You can just choose whatever you want from the hotel specific breakfast menu.. with a "build your own" option for the English breakfast or the choice of eggs benedict or avocado toast. I can only echo the sentiments of
corporate-wage-slave about the pastries, they were excellent. Cappuncico etc were available and they seemed fairly accommodating if you wanted seconds (or thirds!) of drinks or protein with your avocado toast, extra pastries etc. Service on the first day was fairly quick as I was down for breakfast before 0845 but the next day was somewhat painful, it was busy and the service was well intentioned (the staff were lovely) but slow after 0930. Breakfast was served from 0800 - 1100 but can't comment on weekday timings - if they differ.
Location wise is good. There is a tube station practically under the hotel and Paddington (trains to LHR and the GWR network) is a 10-15 minute walk.
Overall a solid stay, and I'd be back although I'd probably want to try other properties first. One criticism is the fact that the heating was on in the public areas, which made it stuffy. Although in room the AC functioned perfectly and the windows do open a little.
Hotel exterior:

Hyde Park entrance is just over the road from the hotel:

Single room, 6th floor:
Walk in shower with shower pressure that goes up to notch 11:

View from the room:

Breakfast area:
Breakfast menu:

Eggs benedict:
Avocado toast: