Dicentra Spectabilis

Look under the pot. Are roots appearing?
If so, repot to a larger pot, and while doing that, incorporate some compost/manure in the mix.
If not roots appearing, topdress with same or granular fetilizer, as this will help the plant to build up strength for the winter.
If you intend to keep it in a pot, protect it over winter - the pot that is. Surround with anything that will insulate, even crunched up paper. As with all container plants = protect the roots!

This plant is quite hardy in Surrey. I suggest planting it under the canopy of a deciduous shrub or tree as it likes shade. It should die down completely over winter and the shoot up again in early Spring. If you have nowhere to plant it, put the pot under some tree shade and raise the pot off the ground on feet or bricks to improve drainage over winter.

Disagree strongly with part of what Burgundy has said - do not feed at all this end of the year, particularly not with a nitrogenous feed as suggested. It would also be better if you could avoid repotting it till next spring, though if the roots are hanging out the pot, you may have no choice. Potting compost contains nitrogen too, and nitrogen promotes leaf growth, which you most certainly do not need or want at this time of year.

oooh - I love disagreement Bamboo. I do agree with what you have said, but I find that the natural chemistry of a plant, will always over come the unnatural. That being, any young growth that does emerge, will naturally die off, as it is herbaceous. This, as you will know, is of no problem. What is more suitable, is that feeding will induce a greater and stronger root system, and if this lovely little perennial is to remain in a pot, the stronger the root system the better, to fight against the cold.
Not that it matters really; everyone has their own little ways, and nature has it's own little way of beating all of us; hopefully tbough, for the better.

Cool answer, Burgundy, respect!

Thanks Bamboo, my pleasure.

Well thank you both for all that information - I didn't expect a debate, but am very grateful, because as usual I have learnt something! I am going to keep it in the pot, as the roots are not coming through, and I will not feed but give it some protection over winter as Volunteer suggested - would it be ok to stick it in an unheated greenhouse and make sure I water it? Cheers, M.