I was actually on the Glasgow flight last week my first ever flight from Knock. I was surprised that it was almost full, that was during the week and I came back on the Sunday but it was maybe 60% full. So it must have its good and bad days.
Regarding Ryanair coming back on the LGW flight I think it would be good both airlines offer completely different services. XL is kind of in this day and age a full service airline they don’t charge for bags.