Thunor
Obtaining references for the security pass does not require that you be employed for the past 5 years. You just require a reference from anyone who has known your wherabouts (and is not related to you). It will not be a problem I can assure.
As for what to wear I dont think anyone from easyjet will look disapprovingly upon what you consider to be appropriate for a BA interview. I do believe though that easyJet look for those with team working skills above those that know how to apply make up correctly.