RobJean
The key issue will be whether, at any time, you need to make a new claim for HB. If you do then you will be forced onto UC, however, if you are able to continue your existing claim for HB then you won't.
You can make what is called a nil income claim for Housing Benefit but I am unsure whether this can be done without you having to claim UC, contact your Local Authority to see whether it will be accepted or not.
If the Decision is not revised at the MR stage and you go on to appeal then you can ask for your ESA to be reinstated at the Assessment rate and this will allow an HB claim as well.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems