My limited experience with the Grand is that they, like most British hotels, will put you in the worst room your rates qualifies you for even if the whole hotel is empty. You have to keep demanding to switch, very possibly more than once, to end up somewhere decent.

The Sign is not a luxury hotel, it's not even an upscale hotel. It's a Holiday Inn-style convention hotel. I would not call either the Sheraton or Radisson 5* but they are better than the Sign.