This is really simple

Sign up for the basic package below, which is only £99 and includes the publication of an eBook edition.

Then later, when you want to add the publication of a paper edition you just pay the difference.

Publication of a Mono (B&W) book with [40 – 100] pages* and with a maximum of 10 images (Estimated printed edition per copy cost to author £2.00)
eBook Option1 £99

* Based on A5 page size.