An A2 bike would be ideal - something like a Honda CB500, Suzuki V-Strom 650 or Yamaha MT-03. All reviews for motorcycles and scooters are here: kit.honestjohn.co.uk/category/scooters-motorcycles

Perhaps even an electric bike like a Zero FXS (kit.honestjohn.co.uk/reviews/review-zero-fxs-2017/) if you're worried about the London ULEZ, then you can charge it at work or nearby. Generally, we'd recommend a naked or adventure style of bike for commuting as they keep the weight off the wrists and give good forward vision from the seating position. Also, it's worth putting a couple of crash bungs on in case the bike gets knocked over when parked - a sad truth of commuting in London.