I would either take the HEX to Paddington then a cab, or the Tube all the way. I don't see any point in taking the HEX then faffing about on the Bakerloo Line.
If you're taking the Tube all the way, I'd do the following:
- On alighting at Green Park, DO NOT follow the connections sign for the Jubilee Line. Instead, follow "Way Out" which will take you to an up escalator. When you get to the top, instead of going out the barriers, go back down to the Jubilee Line (left, I think, and two escalators). This will save you all sorts of stairs and long corridors.
- At Bond Street, you can get the escalators all the way up to the ticket hall. There is an exit that will take you to the correct side of Oxford Street for your hotel, but, if you have heavy luggage, I'd instead recommend that you exit via the mini shopping mall that the station leads out on to. You will then need to cross Oxford Street, but will have avoided any stairs.