Wallflowers (Chieranthus) are perennial, only biennial on heavy soils. However, the norm is to grow them annually and treat them as biennials. Sow in May, plant out in October and discard after flowering in late spring. You may get a minor flush of flowers in a mild winter if your plants are well advanced.
It seems you have the choice of clearing them out to make the space you need or leaving them to flower again in spring. I think the ideal would have been to have had some young ones to plant out as mentioned above, taking up less space. When they do overwinter they become woody and leggy anyway.

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whip them out and buy bare root bunches of wallflowers (usually around £1 for 10) to plant in September for next Spring. Garden centres stock up at the right time so get some and maybe some bellis and aubretia when you plant your spring bulbs.

Wallflowers in general need a cold period-ie winter to initiate flowering so once your wallflowers flowered spring they wouldnt flower again in general until next spring-this however doesnt apply to a variety called Aida which has been around a few years now and will flower in Autumn and right through into spring and beyond.
If you are going to replace your wallflowers as suggested by others make sure you get some good ones-some bareroot plants are dire.

I think they flower in spring and autumn.

Since you pruned them, hang on until winter and let us know how you get on.

It is best to replant each season with fresh stock from a reputable source but you can get seed from the flowers if you hang them upside down in a paper bag in the ceiling of your shed, when the pods have fattened.

The green sap will drain from the stems into the seed and allow them to ripen. The pods will open and the seed fall out making it easy to collect.

Mix with dry sand or peat and scatter according to the instructions for seed sowing found on the back of the pa... errr...

thank you to all of you - very helpful advice indeed from all of you. I think I'll follow all of it; I'll clear out most of the wallflowers (consensus view) to create space and light for my other plants, but leave a small amount behind to see if there is an autumn flush and hopefully I'll let you know how I got on as requested by weatherlawyer.

I row the boat with Plantzzman, If you want to keep wallflowers for a second season they should be cut back to about 3 inches after flowering to produce new growth for the following year.
Do be very careful when buying in new plants and remember to check roots if possible for any signs of clubroot.
Best wishes,
Gerald.

Weatherlawyer,this method fo ripening wallflower seeds is interesting. Can I do this for other flower seeds. I always miss seed collection because I wait too long for ripening and then they are all scattered.