134 to Torrington Place or Chenies Street stops, both on Gower Street. Then just walk across for like less than 5 minutes. I used to live extremely close by there last year (I'm at UCL not SOAS though). Doesn't take too long in the off-peak. The 390 stops at the same place. It's usually a bit quicker.
The Opal 4 is huge, and loads of students live around Tufnell Park and Archway, so you certainly won't be alone.