...an application for instalment order...
Yeah, do that.
As to the Application To Set Aside, while you can bring that application (assuming you are still in time),
you will need exceptional and unusual grounds, or a point of law, for it to succeed.
Arguments such as "I never received the Claim", "I got the dates wrong", and "I didn't understand it"
can, but almost never actually do, succeed.
Understand that there is no automatic stay on the existing order,
and that if you fail to comply, you may face further action for that breach.