DD 22mths keeps saying go away (not picked up from home!) and just wanted some advice on how to handle this as not something I want her to make a habit of saying.

When my DD says that I try to ignore it. Don't turn it into a big deal ('you don't mean that'/'why would you say that' etc.) If you respond she'll soon learn that it gets a reaction and do it more!

I've realised she usually says it when she's tired or when things are changing (time to go home, time to start getting ready for bed etc.) so I try to give her some space.

What's the sort of context in which she says it? Does she seem sad/frustrated/angry?

tends to do it when tired and grumpy and watched her reaction today when I said no-she liked the attention. when I turned away and ignored it stopped her much more quickly, so looks like the way to go.

Dd also did this at that sort of age. We just said things like 'that's not nice' and moved onto talking about something else. She doesn't say it now.

Good to hear. Found the turning away and not acknowledging has really helped.

If you don't like that turn of phrase choose another and explain that when she says go away.

The sentiment should be similar imo, after all we all feel a bit like sayijng go away sometimes don't we? so maybe, "no thank you" is preferable???

When she says; go away
you say; do you mean no thank you? no thank you. okay

and respect her wishes sometimes, to get the idea across. (and cos it is good practice )

I agree slur. She is only 22m after all and will use whatever she can actually say to express her feelings. So it may be it's not the sentiment, just a tool, iyswim.