How long have they been sitting in their current location? For Carex, which lasts from 3 to 5 years, if it has been about 3 years in its current location, it might not survive the move for too long, mine did not. Stipa which I think is a warm weather grass is best moved in the fall. Try to plant it in a location which has similar light and soil conditions to lessen shock. Please wait to hear what others have to say to come to a final decision since I am from the USA and not the UK.

my experience of carex is that as long as the ground isn't waterlogged or frozen it will transplant quite happily any time of the year. I have always moved them with a good amount of soil around the roots

don't grow stipa though so not sure.

The recommended time for moving any of the grasses is early spring. That is when they begin to grow new roots. Any other time and they have to rely on the roots they retain when they are moved.

Thank you all, Loosestrife, Eileen and Owdboggy. I appreciate all your feedback and advice.
I'd planned a few summer of 2020, they're quite close to each other now, obviously having grown. I'd like yo move one or two to another location, which means I feel like I've gained a couple of plants, sort of free!
I'll wait til springtime to transplant them.
Thanks to you all again.

Are you intending to divide any or move the whole plant?

Hi Loosestrife, I thought I'd move the whole plant. There not massive as such, but, I've quite a small garden.

Hi Kate, Happy New Year! I don't have much to add, but whenever the plant nurseries are stocked and/or shipping, then it's OK to move/transplant of course carefully to prevent damage, but none of us are perfect and they usually pull through just fine.

Happy New Year, Paul!!!! Thank you for your message and advice - always appreciated!
Best wishes for a much happier and healthier year ahead of us!

Thanks Kate and you likewise. Our health is most precious over everything else. Let's be good stewards and part of the solution.