Pro: location, value for money, check in communication, the staff are friendly and they looked after our luggage before we checked in and after we'd checked out. The way your room and door core is texted to you is pretty cool too.
Cons: if you have heavy luggage you have to lift them up a tight, old school staircase, our window had a crack that had been cello taped but it was loud and had a large draft. No bedside table/lamp/light that wasn't as bright as main light. You'd be surprised how often you use low level lighting!
Despite this, I'd happily stay here again. The staff were kind and the room was fit for purpose. If you've got a short trip to London, this is the place to be!