When we went it was a bank holiday weekend and we couldn't get in. To be honest we only just about managed to get in somewhere else before it filled up – it was August last year. We then upped sticks and moved to Castlerigg on the Monday morning (was in the lakes for a week).
I guess if it is high season and you turn up late on a Friday you won't get in – the gates are locked at either 8pm or 10pm so no cars can get on site, though there is a little parking outside IIRC. If it is, say, Thursday, you may be OK. They may be able to tell you if you give them a bell.
Yes the pub is the one that sells vegetarian food but it is really pants (and hideously expensive). It could do with more than a lick of paint, a menu that has come out of the seventies (lots of Chinese food, I recall) but it isn't that far to pop into Keswick itself. I recommend the Square Orange cafe, it's pizzas are really good!