They are definitely not at their best in pots. I'd cut out all stems except for the few young healthy ones coming from the base, and plant it out. It will produce new shoots and look healthier. I think it might be E. x martinii, which I think thrives best in a little shade or at least not in the hottest driest location. They aren't long lived plants but they do self seed to replace themselves.
"What is hateful to you, do not do to your neighbour".
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Bumping up
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
Thanks for advise Verdum. It sounds like they'll recover in their own time.