I'm told you could also take the Elizabeth Line from Heathrow to Paddington and it could be much cheaper (unless you pre-book your HEX tickets at a highly discounted rate), although a little bit longer (since it makes a number of stops in between). I've never done anything but HEX, so can't speak about what this ride is like myself.

Until they connect the Elizabeth Line all the way, you will arrive at one of the platforms inside Paddington regardless of whether you're on the HEX or not. You will then need to get off the train, walk out of the station and go underground for the Elizabeth Line trains out to Canary Wharf. The entrance is right outside Paddington, and it's still covered in case of rain, but please keep this in mind. At Canary Wharf, to get to this hotel, you'll want to exit towards the back of the train if I remember correctly. Once you go up the escalators to ground level, turn right, go over the tiny little bridge and turn left on the boardwalk along the water. The hotel is immediately on your right as soon as you pass under the DLR tracks. You can either walk down to Hertsmere Rd. off the boardwalk by walking between the hotel and the DLR tracks (it's not pretty -- you go past the hotel loading dock), and then turn left to the hotel entrance, or you can continue straight on the boardwalk as if to go around the hotel and turn right. There's a hotel entrance immediately to the left of the entrance to the hotel's restaurant (Montana Grill or something like that). The doors open to a long hallway, at the end of which is another set of doors that take you into the hotel lobby. The advantage of this entrance is that it brings you in at the lobby level, whereas the Hertsmere Rd. entrance is a level between the lower level of the hotel and lobby level, and you have to take the stairs up to the lobby or a ramp down to lower level and then the elevator (lift) up to the lobby.