St Marys RC Primary School, looking for advice

We'd love to send our DS to St Mary's. We are practicing RCs and whilst we do attend church regularly we still worry about the strict weekly attendance for 3 years requirement. Would anyone have any advice on whether they think that getting a nursery place there will increase the chances of being offered a place at Reception level? The admissions process states that having a nursery place does not give priority or guarantee a Reception place, but I still wonder whether in practice it would increase our chances and therefore be worth applying for and moving DS from his current nursery if we get offered a place?