MQ as a whole is pretty damn close to the station, less than five minutes. Depending on the actual building your heading to it can be anywhere between 5-20 minutes. As a very rough guide (from the station):
C blocks: 10 mins
E Blocks: Mostly a 5-10 minute walk, but if your in E12 or E14, 15 mins
W Blocks: Mostly 15 mins but if W19 or W21, 20 mins +
X blocks: 15 + mins
Y blocks: 20 mins +
F blocks: 5-10 mins, getting to F9A can take a bit longer