I should be preparing STAR type responses. I feel very out of my depth.
hope it goes well.
as for the STAR thing - is there a specific list of requirements (either technical experience, more generic experience, behaviours or whatever) for this job?
the STAR questions ought all to be about things they have asked for in the job advert / description / person specification rather than things they pluck out of the air, and depending on circumstances, examples from outside current job or even outside paid employment can be a relevant answer (for example the planning, research and time management involved in doing a part time higher education course might be good examples) - it may be that the skills / experience that make you right for this job aren't all skills etc from your current job.
it can be a 'give us an example of a time you did this specific technical task' or 'a time you managed a project to a deadline' or 'a time you delivered excellent customer service' or something like that (i'm not sure i know - or can remember - what you do, and don't know how related this role is to what you do now)
it's probably worth re-reading and thinking of an example or two for each one, and if you can come up with ones from different situations, this may help show more broad experience. but yes, giving one example of X can advantage people who are good at bullshit and not give a chance to show a broad range of experience.
remember that the situation is about the organisation / team, the task / action is about what you as an individual did to make whatever it was happen.
personally, i'd say not to try and rehearse them word by word - sometimes they will add a twist like 'and what would you do different another time?' or 'and what did you learn from this?'
like most things, it's variable. i've had competency type interviews that have been more like a natter down the pub (although without a pint to hand) about work i've done in the past, and them talking a bit about what they do, and these have often led to job offers. i've had others that have been some HR nurk who doesn't know anything about the job asking very narrow questions and basically ticking off buzzwords against their checklist.
and is this an internal vacancy, or just circumstances that other colleagues are going for it? if it's internal, don't fall in to the trap of thinking you don't have to tell them stuff because they already know you / what you do - unless they specifically tell you otherwise, assume they are scoring everyone - internal or external - on the same basis. and likewise don't be afraid of repeating stuff you've put on the CV and / or application - sometimes that is used for shortlisting, then the score in the interview is the only thing that counts.