UC housing costs and service charges

I live in a housing association shared ownership property and am moving from ESA and HB to UC. My landlord (housing association) has told UC a lower figure for my service charge than what I actually pay - they have not included the £20.83/month contribution to the "sinking fund". My Housing Benefit has always covered the sinking fund. It pays for things that would otherwise become eligible charges anyway, like cyclical maintenance. I have to tell UC that I agree with my landlord, or persuade my landlord to change the figure. Is there any way I can get this charge covered by UC, as it always has been by HB?