What's the process to get my job back after mobilisation?

Your former employer is legally obliged to take you back into employment after your post-tour leave. You should be briefed on how to apply for reinstatement as part of the demobilisation process. At the same time, you'll be given a copy of Guidance for Reservists Returning to Civilian Employment: Procedures to Secure Reinstatement  (JSP 532), which you should read carefully. The guidance tells you how long you've got to write to your employer applying for reinstatement, and provides template letters. You should also think about going to see them in person