About the tweet, Thorpe park was also replying to people on Facebook saying the exact same thing. But since then, on Facebook they said on the 18th of May...
Slammer is undergoing extensive refurbishment and we hope to announce details real soon/ Thanks
On my visit on the 25th of May, I asked a member of staff that I knew from last year who worked on Slammer and he said that Slammer should hopefully open tomorrow, if not on Tuesday. Obviously this hasn't happened but it just proves it is ready to open very very soon.
On Wednesday it was testing all day, although it was a lot louder than it has been in previous years. https://www.youtube.com/watch?v=eP9KUdmgx_Y
Hopefully we will see Slammer open very soon and hopefully it will stay open for the rest of the season