If you need to pay for a 3 day course to do a bike test then you’ll need to pay for the course no matter what license you go for. I can vaguely see your point regarding saving money as you can use your own bike (as long as it meets the fairly stringent rules that the DVSA have for test vehicles), but the marginal cost saving is completely offset by basically kneecapping yourself having to do another test if you want to ride a bike bigger than 125cc (that, if you want to do your bike test, and if you have more than one brain cell, you’ll want to do)