Rosebery Hall provides a great breakfast and can offer excellent value for money for a stay in central London. Rooms are quite basic, with no TV or coffee making facilities, and the shared kitchens don't always have mugs, glasses, etc. (and don't provide tea, coffee or milk). My bed felt like it was missing a few springs and there was only one, quite thin pillow, but I slept well enough.
The shared shower/WC was a little odd, with the shower doors only going to shoulder height, and then a shower curtain on the inside of the door. You had to hang your clothing over the door (no pegs or dry place to put them inside), and any footwear outside in the communal area. I think my landing was single sex (men only) but there was nothing to stop anyone trying to use facilities on other floors.
The Hall sits on frequent bus routes and has a TfL cycle hire station close by (Hardwick Street), but is a few minutes' walk from the nearest tube (Angel). There are plenty of pubs, cafes and convenience stores nearby.