Staining/varnishing stairs

[Squeekycheeks]

Hi, I am in the middle of sanding my stairs, not the steps, just the banister and spindles etc, and would like some help on what to finish them with please. They are pine but were stained quite dark, I would like to keep them as light as possible but don't want them to go yellow or orange. Can someone help me out with what I should use please, do I need to seal them with something first before varnishing, can I use clear varnish and nothing else? Can anyone recommend any specific products from b and q/homebase/ screwfix, thanks!