That falls under cheating and can get you banned.
As a fellow UK player I can tell you it really isn’t that difficult to get Rare DNA sitting at home. I do it all the time. Use scents, especially the giga and rare ones. As a level 20 player as well, I can confirm that combing DNA to create a Rare hybrid does work towards the Rare DNA goal. I do it all the time. If that isn’t working, then I recommend contacting support and reporting that as a bug.
The other thing is that the Rare requirement usually only comes up (in my experience) on days when Rare creatures are more commonly sighted in the wild.
Edit: Also, you can go out walking as part of your daily exercise. I play JWA doing a walk around my neighbourhood.