This is probably a bit random and what I am really asking is about being more assertive at work, but I'll explain the situation for background info.
I am an administrator for a large team, based in an office where there are lots of other teams as well as my own; none of these have their own administrator, so I do bits and pieces for them as well. The things I can be asked to do are fairly varied, but I would not be asked, for example, to come into another team's meetings and take minutes, or to do a letter for someone. I might proofread a report for my own manager, though.
My issue is that my predecessor in the job treated it as a much more traditional secretarial/PA role, almost in a 1960s sort of way. She would do things like making tea for the managers (I'm happy to do a tea round but I don't see it as my job to "look after" my boss with hot drinks), setting up meeting rooms for other teams with water jugs and biscuits, organising social stuff for everyone, etc. She's still around, as she got promoted into a different role, but she does often ask me why I haven't done X task that she used to do which I don't consider to be part of my job. I would be able to handle this OK if it was just her doing the asking, but some of my other colleagues who were around when she was in the role also keep trying to give me jobs to do which are really not supposed to be in my remit.
I realise that this is probably making me look rather difficult and stroppy. I promise that I'm not - I am professional, and widely considered to be good at the job. I have no issues at all with doing the things that I'm supposed to do and helping out with other stuff when I have the capacity. But I am also not at all keen on being the little woman who runs around facilitating everyone else and acting as the tea monitor! Some of the older men are downright lazy with some of the things they ask me - it's just a habit that they come to me as a first resort instead of trying to do anything for themselves, and I feel like this has come about because they've got used to being coddled.
I know I need to set some boundaries but I just need some advice on how to do that without upsetting anyone. I still need to work with these people, including my predecessor, and I don't want to come across as implying that she was doing the job was wrong, just that my way is different.