do you ever have to trim a chilli plant

Hello Irishchili,
I'm not sure what exactly the problem is. Do you have some stems that have no leaves? Is it just getting too big for the space?
Where I am chilis and other peppers are treated like annuals, they grow one season and you harvest them and then start with new next year so pruning or trimming isn't necessary. My guess is that if a stem has no leaves on it you could cut it off, because another should grow from a lower nodule or stem branch, just like pinching back an annual flower for bushiness.
A picture and idea of the conditions (where in the US are you) would help to give a better answer. Hope this has been of help.