Hi itsme I'm coming at this from a different angle. I worked in a LA Children's Services for 25 years (the last 15 was managing an Adoption and Fostering Team) Retired in 2004 but worked independently till 2009 and then retired completely.
I think you have had incredibly good and thoughtful answers to your post, from the adopters which I'm sure you'll remember. I wasn't totally sure whether you are applying for a post as an adoptions social worker in an Adoption team, or whether you are applying for a "post-adoption" social worker. I hope it's the former.
Thinking of the interview, I picked up that you are feeling like a "newbie" and in a sense you are, but I think you will need to talk about "transferable skills" from the Adult Services team that you can bring to the Adoption Team. A lot of people in interview talk about what they have done in their previous job instead of thinking themselves into the job for which they are applying. This will be difficult for you but you can be honest and say that you know where the gaps in your knowledge base is (bit of jargon there - which I hate incidentally) but they seem to like it at interviews!
Looking at those gaps, I think first and foremost is that you don't have any child protection experience and to be honest that is quite a gap, because you won't have very much idea of the reasons that children get into the LA system and end up with a care plan for adoption. It will be difficult to talk to adopters about these children and the reasons for them being removed from home etc but you can talk about ways of "plugging the gap" by discussions with duty social workers or members of the cp teams (if they have time!) reading files and maybe going out on visits with cp social workers and of course reading around the issues.
Ok then we come to the task of the adoption social worker will I assume be primarily to recruit and prepare/train prospective adopters, and carry out PARs (as they are now called - Parent Assessment Reports) they were Form Fs in my day! Present your families to the Adoption Panel, and be involved in matching, liaising with the child's social worker, being part of the intros and offering support throughout the adoption process, and post approval training and support.
As far as prep/training groups are concerned, you could be an observer at a group carried out by adoption social workers and I think you would soon pick things up, and will be interesting for you to "dip your toes" in so to speak before you are running your own courses, though we always ran courses with 2 of us, and invited children's social workers, experienced adopters, a clinical psychologist etc so you are not alone, but planning a prep group takes an enormous amount of time, take my word for it!
Moving on to assessments, well you begin assessing the minute you first speak to someone who is interested in adoption don't you (I'm sure you do this in adult services) it's 2nd nature isn't it really, it isn't always conscious but nonetheless that's what's happening. I haven't seen the new PARs but I imagine they are much the same as the old Form Fs and there will be a lot of factual information to be collected, but dependent on how the LA organises itself, a lot of the information gathering can be done by the applicants and admin workers.
The real work of the assessment is about working out whether this person, couple have what it takes to become adoptive parents. Applicants are often worried about the assessment and so as others have said you need to be able to put them at their ease (and don't ever let on this is the 1st assessment you've ever done..!) Somehow it's less complicated with a single applicant, because with two applicants you need to be assessing the dynamic of the relationship between the 2 of them, and this can be shown in their body language, how they respond to issues, and how they interact with each other - if one is very talkative, then I would always look at the less talkative one to see if they were comfortable with that or whether they were uneasy - or even embarrassed. I'd be wary of people who claim "everything in the garden is rosy" because it never is.........life isn't like that, but you might have to give them "permission" to talk about more difficult stuff............look I'm going on and on here and you probably know exactly what I mean because you are already a social worker and will already have those assessment skills. One thing though which I hope the PARs addresses (and I think it does) is the social worker's analysis of a situation and this was so often omitted. We would get reams of stuff about the information gathered but no analysis and that is the essential skill of assessing. Anyone can collect information, it's what you do with it that matters.
I think there is a definite move towards competency based assessments (there certainly was before I retired) and looking at the skills applicants already have and can evidence, which is really helpful and gives credit to the applicants for their own life experiences, especially child related ones.
I think I've probably said enough! The trouble with interview since equal ops (I much preferred the ones before equal ops!) everyone gets asked the same questions. I found them all rather stilted and we didn't get to know the applicant like when we could ask about relevant issues and sort of draw the applicant out..........so I'm not sure if you will get the chance to make some of the points I have raised, that's if you think they are valid of course.
Finally, I might be wrong but I'm picking up that you are a bit apprehensive about this interview and of course that's only natural, but you might need to come across as more assertive than you are sounding at the moment! Be honest about the gaps but talk about ways you are going to fill them. Ask the adoption team for some of the BAAF publications that they get on a quarterly basis (well I assume they do, as we got loads of stuff from BAAF - which I never had time to read!) but their booklets cover a wide range of topics and you could go on the BAAF website and mug up on some issues and "Adoption UK"
Best of luck and be interested to hear how you get on.