To make this recipe gluten free, replace the plain flour with a good-quality gluten-free all-purpose flour blend that is designed for baking. It is best if the blend already contains xanthan gum; if it does not, add a small amount according to the package guidance. Also make sure the baking powder, bicarbonate of soda, chocolate chips, and any nuts you use are certified gluten free, as some packaged products may contain traces of gluten through cross-contact. The texture may be slightly more delicate than the original loaf, so allow the banana bread to cool fully before slicing to help it hold together better.