Hi Danny, There's a few council run halls available – it depends what size event or gathering you've got in mind.
The Walton Centre in Manor Road is good and very central (01932 247539) but may be can't cater for too many people. If it's a big gathering you might want to think about the Playhouse (it's behind the Aston Martin garage) and holds may be up to 200 people and has a bar. Parking is a little bit limited but there's a car park across the road (01932 254750).
I'm not sure what pubs in Walton offer in terms of function rooms but I know The Inn on the Lake at the Silvermere Golf Club at near by Cobham has a number of rooms of various sizes, has a bar, can cater, has loads of parking and is a good location for people coming from further a field as its just off the A3 (01932 584300). Hope that's all of some help.