For a while a lack of green space has been a problem at Thorpe Park, particularly since Stealth has been built the park has developed a very claustrophobic feel.
One of the best places to "escape" the crowds for a bit of peace and quiet is the grassy area in Lost City on the edge of the lake in front of Vortex and Zodiac, just next to the Crust snack bar. I would imagine that even this gets busy though on hot summer days.
Other than that and the Sunken Gardens however, I can't really think of anywhere else asides from the odd grassy patch in front of Storm Surge or by Colossus' final turn. The square around the teacups tends to be quiet and there are lots of benches, but it's not the nicest of places.
It's obvious that the park has developed too quickly without enough thought for creating a proper infrastructure that caters for guest needs. There are lots of 'dead spaces' in the park which are unsuitable for new ride development but would makes good social areas. For instance the area from the Boardwalk Games arcade up to Rangers County (in front of the arena) could be redeveloped to create a plaza in the centre of the park with with a landscaped seating area. At the moment it is just lined with rubbish games stalls.
I once remember seeing a plan for Nemesis Inferno (drawn up by John Wardley I think) which showed a plaza area in front of the volcano, alas what we ended up with was simply a large paved area which is good for nothing.
Back to the topic in hand.....I sure hope that the park will quieten down in the next week or so, but you just never know with this place. I think the weather is a big factor.