I'd better start the ball rolling. I've some verses here and a couple more in the pipeline, not too great at the humour however.

Will we stay or will we go
to buy and sell via the WTO?
Maybe we can join the EFTA,
stay in the single market
but without much say
You know we've got, got the indecision blues.

Farage says "We're British, we do as we please;
You never ever worked", he told the MEPs
That made the Europeans hiss and boo
"You don't like us; hell, we sure don't like you
You can go and get, get the separation blues."

"It's time," Farage says, "to put Britain first,
Get out from under Europe's thumb.
It's better to go then be besieged by the migrant scum"

"Leave the union, better leave it quick
Leave the union, better leave it quick,
Leave the union, leave it quick
If you voted for Brex-it.
It's time to get, get the separation blues."

"We're better off out," said Johnson to Gove
But when Leave won the vote, Mike gave Boris the shove.
We thought they were the best of friends
But Boris hesitated and that was the end
And now they've got, got the separation blues.

Which only goes to show, since it all began
The referendum was a power game
Leave or stay, the people are sold,
Politicians act the same.

"Leave the union, better leave it quick
Leave the union, better leave it quick,
Leave the union, leave it quick
If you voted for Brex-it.
It's time to get, get the separation blues."