We ran through the booking specification at a high level, including checking the direction taken on remaining issues. Everyone was broadly happy, with some comments to raise on GitHub and a suggestion to consolidate cancellations into a single PUT call for the Order (to allow for atomic cancellation, given the potential for additional cancellation constraints to exist).
As a result of the call we:
Clarified the spec regarding the error raised when attempting to book a non-"bookable" opportunity.
Amended the spec to make cancelling multiple items atomic, with an outstanding question regarding restrictions (https://github.com/openactive/open-booking-api/issues/102)
Raised and linked an additional issue: https://github.com/openactive/open-booking-api/issues/103