Hello!
Being an ex Servisair Dispatcher, I can tell you the pay scale is not all that, You will be on the £6 per hour scale, if they are a nice station maybe a little more, but don't expect anything near £7ph.
I really can't tell if you got it or not.. I was recruited for check-in and then and went on internally for dispatch.. When I went back to them last year, the intake was a mix of experienced and non experienced staff.. So you might have a bit of luck! normally they want staff with past experience..
To be honest though, If they phoned back and asked for uniform sizes, That is a good sign, but don't count your chickens just yet..
20 Hours - If they handle Holiday charters at Belfast, then you will be able to secure yourself mountains of Overtime.. maybe see 40-50 hour weeks.
Best of Luck!