probably off-topic: you mention 37h/w so I'm guessing (Western) Europe... Do you find it reasonably easy to find consultancy jobs that allow for ~20h/w (and still make enough for sustenance)?

To me it looks like freelancers are generally accepted by companies only if hiring permanent staff is not feasible, and once they decide to pay the (usually higher) daily rate, they would squeeze so much out of that day that half-day jobs would be blasphemy - unless you're very well known for your expertise in your field/niche, of course...