I am sorry you and Pip are having this experience; it must be quite scary for you to see this happen.

Be cautious about saying Pip has feline epilepsy. From what you wrote, at this time you do not have a diagnosis. You have witnessed seizures, but have yet to learn the cause.

I did not see, how old is Pip?

Other than this, I have no personal experience, to help guide you. I did some quick search online using Google, and it does seem and MRI or CAT scan is the next step. However I also read that often even this does not provide a clear diagnosis. Since the seizures are so far apart, I think I would do as you are doing, search for more info before spending the money on those tests.

I hope someone else will have some ideas to help you.