At a guess, I think the BoE wants, in part,  a more efficient way for the banks to transfer reserve currency between themselves. At the moment it's likely pretty inefficient and done at the end of each day, AIUI, They likely want a system that updates throughout the day, a system that's fit for the internet age, not the legacy system they have now, that's fit only for the age of the quill pen. Seems reasonable to me. I don't see it as a competitor to bitcoin. It'll not make much difference to bank customers other than large transactions might be verified more rapidly. It ought reduce costs to banks and BoE but whether customers will benefit remains to be seen.