Do add in or correct me if I'm wrong, people, but I think the below is how it went (?) ...
Basically, Kate had a trial period as Deputy Manager of Foxhill Indoor Bowls Club last year, where she regularly plays bowls. It didn't go well and ended up with Kate either being sacked or the trial period not being converted into a permanent job - we've heard both 'versions' cited, but either way it ended with Kate having no employment prospect there.
Anyhow, one of her Twitter fans rang up the Bowls Club after Kate had revealed her 'sacking' on social media, posing as a journalist to get the inside gossip. The manager promptly dishes the dirt, and basically says Kate was a mix of incompetent, lazy and useless. The term 'Muggins' comes from the manager sarcastically saying during the call "And I had to work on the Friday, because Muggins here had to come in to cover," about himself needing to cover for Kate, who'd left it with very little notice to say she wasn't available on a Friday.
There's also an element of Val/Mick/Mike 'betrayal', as they were exposed slating Kate's work ethic. My favourite bit was Mick/Mike saying Kate never lifts a finger to help at home.