Post Wedding Party Venue in Cork

My fiancé and I are planning a civil wedding with just immediate family in Cork. However, we would love to throw a party some time after the wedding for all our friends, work colleagues and extremely large extended family. We are estimating 250-300 people.

Does anyone have any suggestions as to a possible venue in Cork? We would like decent finger food or a buffet. Budget is €5,000 - €8,000. I wanted to book the Carlton in Kinsale but they were booked out for a year and a half.
I also thought about hiring a marquee but was quoted €18,000 for just the supply and erection of one.

Thanks

What about using the pavillion of one of the rugby clubs (or GAA) around Cork? The rugby season is finished so they are empty most nights, minimum hire cost as they make their money on the bar which leaves you with the whole budget for food, music and decoaration! Was at a night in Highfield last summer and it was fantastic, they have decking outside the main hall and the band played outside it was such a nice evening!

Thought that any hotel you book that you don't actually pay for the room as such.