Maybe for exclusively UK sales, but any exports to the EU would have to be EN compliant.
Also, in reviewing and updating the old outdated BS 'kitemark' standard, a lot of time and effort (ie: cost) would be saved by just copying/shadowing the already established BS EN standard.
Surely just a case for sticking with the EN , badly framed as it might be, and lobbying for change from within.....that sounds like a familiar argument from somewhere...
All the best,