Two weeks ago we returned from a 2 and half week leisure/business trip to England. While in London we used Marriott Reward points ( booked before the rate increase ) for a week’s stay at the JW Marriott Grosvenor House. It was a lovely stay, great location, the concierge was open 7 days a week from 7am – 10pm with a wide variety of great food, and the service was wonderful. We were upgraded to a deluxe room. It is only about a long block or 2 from the Marble Arch Tube station. It is a great place in central London that is close to so many attractions and a short tube ride away from the rest.
The Park Lane is maybe a slightly better location ( across from the Tube Station ) , but seems to be a little more of a boutique hotel. It looks lovely though and has great reviews.
We also stayed at the Marriott Heathrow/Windsor at both ends of our trip. Actually 3 nights at the beginning because we used it as a base while touring Windsor, Oxford, and it would also work for Blenheim Palace. If you are traveling with family, you should certainly check this Marriott out. The concierge lounge was nothing special, but the entire hotel staff was fabulous – finding out train, bus, taxi, and Heathrow Hoppa schedules - very knowledgeable about all of our transportation needs. If you are renting a car, it is probably more doable from this location than from downtown London. There is a bus stop almost across the street, and a taxi to the Slough train station was only 11 pounds. They have very reasonable weekend rates at this time ( currently 60 pounds/night ) as well as they participate in many of the London specials such as get 3 nights for the price of 2. And make sure that you get the breakfast with it, because it was well worth it. They took such good care of us, that I had to write about it. Of course we also told the management.