Root pruning is quite possible for virtually any shrubby plant but it is normally done in the dormant season. Not sure doing it now is a good thing?

I checked this recently with a bonsai grower as I need to trim the roots of several of my garden conifers that are in pots sunk in the ground to keep them small. He told me that it should be done in spring and it is too late now and will harm the plants. If you have a local bonsai group they will normally be happy to help with any more detailed questions on root trimming and how much to trim and when exactly etc.

My conifers are not bonsai but the same principles apply as I have a tiny garden and have to keep many plants smaller than they want to grow.

MANY THANKS FRACTAL AND WEEDFINGERS I AM ONLY A YEAR + LATE BUT BETTER LATE THAN NEVER. I CHICKENED OUT IN THE END AND LEFT THE BAY TREE TO FEND FOR IT SELF. BEST WISHES DRAKEY