@Cadder Great to hear how well your plants are doing!
On the Choc BBG at this point I would personally just let it run it's course for the rest of the season.
Trimming lots foliage now might deprive the plant of energy it needs for flowering & fruit growth. Having said that you can take off any old tatty foliage and lightly trim new growth to keep it in check without too much negative impact. One option at the end of the season is to cut it right back to about 3 inched above the soil and bring it indoors. It will then grow back form scratch much lower and you can keep it and shape it as a house plant before next season
I have been growing for quite a few years and I started out with plug plants on windowsills just like yourself.
Each year you learn a bit more and get the chance to experiment! Biggest game changer for me in the last few seasons have been getting my potting mix & nutrients right plus using the self watering tubs. Next step is to try some crossing and more over wintering & indoor growing
Always something to try / learn!