Which room did you book and which upgrade did you receive?
2 Twin Cosy, received 2 Twin Classic (one-category upgrade)

How are the rooms?
On the smaller side, so I can only imagine how small the "Cosy" rooms must be! They are a bit dated design-wise and could do with some more lighting but for the most part are well-maintained and still look pleasant. It was nice to have an air-conditioning system that actually did what you set it to do, instead of being disabled for the cooler months or under the hotel's control. The bathroom however was not great, more on that later.

Housekeeping was good to the point of being almost over the top - they would neatly fold clothes that had been left out, organise shoes, tidy up charging cables and even plugged my wireless headphones case in. There was also evening turndown which was almost as extensive as the morning clean. The only other place I've seen housekeeping like this was at properties of a similar calibre in the Middle East - guests from the GCC seem to make up a large proportion of the hotel's clientèle so perhaps this elevated level of service is an intentional part of the offering.

How is the exec. lounge?
N/A, didn't have access

What was good and what was bad?
The Good

• Superb check-in experience. The lovely receptionist noted the room was still being cleaned but took care of all the formalities, gave us our welcome drink vouchers in case we wanted to use them while waiting, took down our phone number so they could call us when the room was ready and showed us to the public restrooms. Fortunately we didn't have to wait long, just as we were about to head out the phone call came through and we were in our room by 11! I always appreciate when a hotel accommodates such an early check-in.
• Small box of chocolates provided as a welcome amenity in addition to the standard welcome drink vouchers (choice of beer, house wine or anything non-alcoholic, we chose a Malbec)
• Large gym with lots of equipment as well as towels and bottled water. They also had a cart by the front door in the morning with towels, apples and water for those looking to go for a jog.
• Location of the hotel is pretty good with lots to see nearby. Hyde Park Corner station is across the road (keep in mind there are some ramps/stairs up and down to cross the road to the station) and from there you have direct service to Heathrow, so we used the tube to get to and from the airport. Lots of good places to eat and shop nearby, one of my favourites was HIDE where I had a very fancy (but pricey) Michelin-starred breakfast.
• Staff were a highlight, everyone was very service-oriented and thoughtful. When they did turndown the first evening and noticed we'd opened one of the suitcases on the ground, they organised for a luggage rack to be delivered. Then when having a cocktail on the last night the bartender was super apologetic when he realised he hadn't provided a complimentary snack with my drink and quickly organised some olives. Little things that I didn't really notice or care about, but showcased the level of service they are looking to provide.
• There were lots of staff too, basically at any hour of the day there were at least two doormen at the entrance and when checking out at 6:45am on our last day they had three receptionists on hand!

The Bad

• Awful shower experience. It's one of the smallest and narrowest shower/bath combos I've come across and somehow they've managed to fit in not just a regular showerhead but a rainfall one as well! To make matters worse it's not even a curved shower rod so the shower curtain keeps getting in the way, thankfully it was all very clean otherwise I would have been pretty grossed out. It was unbefitting of a luxury hotel.
• A 'discretionary' service charge of 5% for regular rooms and 10% for Club IC rooms is automatically added to the bill, I can't see any mention of this in my confirmation emails and even looking at the website now I can't seem to find any mention of it. Like I said above service was good so I didn't contest it but it would be nice if they made mention of it beforehand. My concern is moreso the lack of prior disclosure than the service charge itself.

Value for $ or IHG One Rewards Points? Would you return?
Used a combination of reward points and a BOGO certificate which resulted in an average cash outlay of £182/night, cheaper than many IHG options in central London! Despite the disappointing shower experience I was happy with all other aspects of the stay and would return.

Photos in the spoilers below!