If you register and print a voucher from Days Out Guide then buy a National Rail ticket, you can get 2for1 entry to over 150 top UK attractions, including SeaLife Centres, Thorpe Park, Chessington World of Adventures, Alton Towers and Legoland Windsor when you present both at the attraction. See the full theme park list or the zoo and wildlife list.
Visit their site here for to search for your ideal offer.
You need to print a voucher for the relevant attraction (follow the link above and search for it) AND have a valid rail ticket bought from National Rail on the same day for a single or day return ticket, or within the days of travel for a return ticket.
What if I live near the attraction ans I’m traveling by other means?
It’s worth doing this even if you are not traveling by train as a cheap single ticket can be available for a couple of quid, far cheaper than the entry ticket price (Alton Towers is the most expensive at £51.60 on the gate).
Just stop by the nearest station on your way and pick one up, then present both to get your 2for1. Crucially, your rail ticket must show that you have traveled to one of the stations nearest the attraction. So for Thorpe Park, you need to have a ticket with an end destination of Staines or Chertsey.
The offer’s ongoing, but check the voucher for each individual attraction’s restrictions, as these vary. See the full T&Cs including which tickets are valid.