Some thoughts and, 'the baby?' Spoilers!

I just watched this and it's hilarious. Considine's "Le Donk" is a cringe-worthy but wholly believable, tragi-comic character, even though he's obviously (unconsciously?) channeled Steve Coogan's 'Tommy Saxondale'. This creation apparently pre-dates Saxondale but both characters are individually funny in my opinion. When you consider it's mostly ad-libbed Scor-Zay-Zee is also no comedy slouch either. I actually thought it was James Corden when I saw the trailer but he's an actual rapper, a little reminiscent of the Streets' Mike Skinner, with a rapid-fire delivery.
Anyway, my question is, what was going on with the baby? Le Donk is supposed to rush home to see his pregnant ex-girlfriend bring her newborn baby home (she wouldn't allow him at the birth as she wanted it to be "calm"!) The baby in question is like, at least 3 months old? I thought maybe I'd missed something in the plot and she's borrowed the baby from someone to pretend it was his (this didn't make sense to me either!) as she was scared to tell him she wasn't really pregnant. When they made no reference to it, I was left confused. In the credits the baby is named as Finn Colman which would suggest maybe he's Olivia Colman's real life son, but I still don't understand why Meadows would think no-one would notice. Having written this, maybe he thought it wouldn't matter in the context of the film. And, it doesn't spoil anything, maybe I'm just being too anal and caring about details that, subsequently mean nothing.
It's a great film, (I'm a big Meadows fan)and I'm so glad he's made it as "Once Upon A Time In The Midlands" is a weak attempt at comedy. For anyone watching their first Meadows film, it's a treat, even though his usual film-making style is hardly evident here.