With no indication of ages or make up to age them, then the assumption can only be that they are the ages they are in real life.
Although ages aren't mentioned there are clues. Someone mentioned someone 2 years older than Robert Carlyle playing his mum, so whether he's playing a character younger than him or her playing a character older than her we can presume a script age gap of minimum 16 years, more likely 25, rather than 2.
So what are they saying? What is their reasoning? Are they using make up to age them? If so is their reasoning that no one wants to see those ageing boring actresses, they are not a pull on cinema goers so better to get a young actress whose in the gossip mags in. Or that we can't be expected to look at woman who shows her age so get in a younger actress and subtly age her in a way that she's still attractive and slim and pert but just with a few flatteringly placed laughter lines so our eyes are not assaulted by genuine age?
I can just about get that there is an assumption that women cinema goers still find older actors attractive as love interests, but men won't find women of the same age attractive as love interests so they just think 'ooh, the ladies love George Clooney, let's get him in' then 'ooh, Jennifer Lawrence was voted hottest babe last year by Nuts magazine, let's see if she's interested' but I don't really get the mum thing.
actresses the same age, 54, as George Clooney:
Heather Locklear
Julia Louis-Dreyfus - in the video posted above!
Meg Ryan
Nia Peeples
Serena Scott Thomas
Mariel Hemmingway - she gets a mention upthread too.
Most of these actresses look younger than 54 in the pics I've just seen. Most of them look younger than 44.
George does also look good though. 