I really enjoy London PRO Massage for a deep tissue massage. I've been there a few times, and am always delighted with Jarek's firm massages. He really knows what he is doing and has clearly studied the human body. One thing to be aware of is that it is inside a gym, so if you're looking for a quiet spa experience this may not be the place for you. I personally prefer such a firm massage that zoning out is not possible anyway so its not a big deal for me!
I wouldn't go anywhere else for a sports massage. HIIT, Boxing and an office job takes it's toll on my back and shoulders but Jarek gets me back to normal. A few people have said it's hard to find - but I found it ok. Enter Zetland House and on the left are some concrete stairs which lead to the gym with sofas you can wait on.