HEX to Paddington and a Black Cab. Black Cabs can use the bus lanes which will speed things up. Order your cab in advance using a service like Halo or Comcab though as you will have a long wait during a tube strike. Don't expect a fast journey, central London is often very congested during a tube strike.
If you are able to get on, my second option would be the 205 bus or the no 98 to Russell Square from Edgware road (short walk from Paddington).
Depending on how much and how robust your luggage is, if you are able, you may want to consider walking. The distance is 2.5 miles if you take George Street (which avoids Oxford street); I did the walk to Goodge Street which is nearby a couple of times and it took just over an hour.