Very walkable, would take me about 10 minutes to walk there. You can cheat and get the free hopper bus (number 3) and get off along Portland St but it's just as easy to walk to be honest.
Just head straight out of the main entrance and keep on walking up Piccadilly approach. If you cross onto the left hand side of the road by the Malmaison and walk up passed Shout (clothes shop), pound shop, mini Tesco, Costa then there is a motorbike shop pretty much on or just round the corner, turn left there and you will go passed Edwards, Blue Parrot Grill, the Brittania Hotel (Jennys Restaurant and Wave Bar underneath), Yates' and it's just a little further along on the other side of the road on a main junction with Princess St. If you get to Philpotts/McDonalds, you've gone too far!