Water butt hidden by ivy.

I have a standard size water butt hidden by ivy.  I need to clean out all the gunge from the rooves that has gone into the bottom of the water butt.  When is the best time of year to cut back the ivy to extract and clean the butt and hoping the ivy will recover (and recover the butt)?

Cheers,   Tony.

Thanks for that sensible answer chum.

Cheers,  Tony.