Secondly is the selection process as rigerous for WSOp as it is for Pilot or WSO and does anyone have any stats on pass rates for OASC?
Stats are irrelevant to a single candidate; they only mean anything at the end of the quarter/year etc.
Many on here will have got through an application/selection/training process that has an
almost (but not quite) impossible pass rate, but some have to pass to produce the output required. Assuming you are medically fit and have the minimum academic reqs. then no-one knows if you will pass/fail until you step up and try your best, and no stats will help forecast the outcome for you as an individual.