Usually it would be either the full day (ceremony, meal and ‘evening party’ which we commonly call the reception) or just the reception. No one is being asked to skip the middle part of the event.
Less than 20% of weddings are religious (and a smaller subset of this will be in churches), and I don’t really hear of anyone just turning up at the ceremony of someone they don’t know.
> Less than 20% of weddings are religious (and a smaller subset of this will be in churches)
That's a likely a fair underestimate because many religious marriages aren't legally valid because of various requirements that the Church of England doesn't have to follow as the state church. In Catholic churches for e.g. they need to register the building, then either appoint the priest as an authorised person or get a registrar to come to every ceremony as in a civil wedding. They do usually do this but most non-Christian religions don't bother with this at all and so the couple end up just having a civil ceremony first and the religious one after.
Less than 20% of weddings are religious (and a smaller subset of this will be in churches), and I don’t really hear of anyone just turning up at the ceremony of someone they don’t know.