Hi soulgal
No you won't lose your UC Transitional Protection. Your UC payment including the Transitional Protection is calculated first and then the NS ESA is deducted £ for £.
UC is what is known as a " passporting Benefit " and allows access to various assistance from the NHS and Local Authorities etc. So in some circumstances it may be preferable to keep receiving UC rather than NS ESA.
Closing your NS ESA claim will not affect your LCWRA status.
The NHS has a low income scheme:
www.entitledto.co.uk/help/nhs-low-income-scheme-under-60s Let us know how you get on.
David