In 2008, Thorpe Park was also part of the 2 for 1 ticket promo and if you take the train to Thorpe Park, they had 4 for 2 tickets then. Filos are bargain hunters. We definitely go for the cheapest possible cost. :)
We rode most of the rides apart from the Samurai, baby rides and Stealth which was underconstruction then. We definitely had fun. Even my sister who is scared of anything had fun taking photos of us and riding the merry-go-round. LOL!
To go to Thorpe Park:
Get off at Staines and take the bus that take you to Thorpe Park. It's pretty straight forward plus you will see lots of people queuing for the bus.