I'm not British, so I'm not exactly sure what's being said here:
Right, Ben, heard the big news about Paxo. Oh, right. What was it you did in your gap year again?
Um, InterRailing, month on a kibbutz.
Did you ever travel, like, 100 miles per hour head-first through a tunnel full of pig shit? Because that's what's going to happen to you tonight with Paxman, unless Unless you listen to us.
He will eat you up, sick you out and grout his fucking wet room with you.
Yeah, I have been interviewed on television before, thank you very much.
From this link
Why is Ben's "gap year" relevant? Is this "tunnel of pig shit" expression just there for added vulgarity or does it have some British back story that I'm not aware of? And what is the nature of this grouting expression?