pretty sure luton is still seasonal. not sure if theres more of a chance at being kept on permanent at luton than other bases but u still have to start off as temporary crew.
i dont know much about the rostas at luton, but being rostered for another base doesnt happen that often at all. occasionally u can be called out to work at another base, but again this is rare and they sort it all out for u - taxi, hire car etc.
and first choice is very friendly!