atpl exams
 

Doyou have to sign up with a provider for distance learning or is it possible just to pay for and sit the exams

I believe you have to be signed up to a authorised course, either a full time course or distance learning. I'm pretty sure it's not possible to just to self study and turn up to an exam.

You need to be registered with an authorised school. They are required to countersign the exam application form you have to send to the CAA prior to sitting the exams.

Assuming you mean EASA, the only time you can self certify is if you have an ATP and 1000 hours multi-crew, plus a couple of other requirements. Otherwise, as mentioned, you need to be signed off by an authorised school.