Toby - if you are typed on A320 and joining as DEC then 95% certain you will be on A320.
Caras - if your tattoo's are not visible when dressed then no problem.
Jonbj - they will put you in final accommodation. Unless if you are an SO then you will share a 2 - 3 bedroom apartment with another SO till your final line check. Exemption is if you are an married SO then you will get a 2 bedroom apartment followed by a 3 bedroom after your final line check.