While sloshed and leaving the restaurant/bar at the end of the evening with Portia, Jack is singing I'm Forever Blowing Bubbles, which is the West Ham United fight song. It's actually also quite a sad song (as oddly, many EPL teams' fight songs seem to be):

I'm forever blowing bubbles,
Pretty bubbles in the air,
They fly so high,
They reach the sky,

And like my dreams they fade and die!
Fortune's always hiding,
I've looked everywhere,
I'm forever blowing bubbles,
Pretty bubbles in the air!
United!
United!

It seems like every character on this show has dreams of something that they find are fading and dying over the course of the trip:

• Tanya wants an Italian fantasy with a husband who adores her, which fades as Greg turns out not to be that person
• Harper wants a partner who wants her and is a match for her, and Ethan being that is fading fast
• Valentina wants romance...which she kind of gets briefly, but I think she wanted something more real than what she got
• Portia wants to be satisfied, but she hasn't found the balance of what she wants
• Bert wants to find a connection to family, a mother figure to accept him, and loses that dream

Etc.

Also, I can't recall where Jack said he was from in the UK. It'd be interesting to know if West Ham would make sense for where he's from or if it's something the show inserted into his character because the song fits a theme for them. Granted, fandom in the EPL is sometimes hereditary vs. area-based, so I guess it wouldn't matter.