Closing CB ESA and request for UC instead

I am an appointee an adult who has LD.. They are migrating to UC and I discovered the CB ESA will continue. They an underlying claim for CB due to migrating from Incapacity Benefit many years ago. Theu have never worked nor will ever work. I'd much prefer all monies ho via UC as having so many different pay dates is a faff. DwP ESA says I can close the CB ESA ( now NS ESA).claim without affecting transitional payments( they have SDP) but I am fearful this would be trigger a change in circumstance.and loss of transitional payments.Any advice or pointers to where I can find this in writing. TIA