My suggestion would be to book a double room and inform the agency/Indy of the name then she will have no problem gaining entry to any hotel.
Sorry to disagree Sasha but the Hilton has security and I have been stopped before. The jury's inn is another hotel employing security as does the holiday inn express and the travel lodge, the security are normally present from 10pm on thurs/fri/sat.
For discretion purposes you can't go wrong with the Vermont, Mal Maison or the Copthorne. On the cheaper side of the market a hotel such as marco Antonio in Ryton is ideal as it has a seperate block to the pub and a discreet covered car park.
You will find though booking a double room for 2 guests is more or less the same price and is probably the safe proof method.