Hi Rosie,
They are really spectacular plants aren't they!

Callistemon don't require routine pruning, but can certainly be pruned either to re-shape them (they can get rather leggy and top heavy) or to maintain them at the size that you require. The time to prune is immediately after flowering. If you don't need to reduce or re-shape your plant then it is also beneficial to cut off the faded flowers (i.e. the last 6 inches or so of the stems that have carried flowers) which will also encourage more branching and a bushier shape.

Unless you are in an extremely cold or exposed position your Callistemon will not need to be brought indoors for winter at all. 'Splendens' was selected and named partly because it is reasonably garden hardy, provided it is given a sheltered sunny location. Of course since yours is (presumably?) in a pot then you can move it to the most sheltered location available for winter and then bring it back to where you can see it once all danger of frosts have passed.

brilliant- thank you

I have a 'Splendens' Callistemon CItrinus which was a present from my son. I appreciate the advice you gave Rosie, it was very useful for me, I love this plant and thE flowers on it are amazing. The worry I have is that my plant has a sort of White 'furry covering' on a lot of the leaves and and stems of the plant. Can u tell me if this is normal or is there something wrong with my plant. Hope u can help, thank you.