  We analyse $B\to K^\ast \ell\ell$ decays in the region of low hadronic
recoil, where an operator product expansion (OPE) in $1/m_b$ applies. Using a
local model for charm contributions based on $e^+ e^- \to hadrons$ against the
OPE provides a data-driven method to access the limitations to the OPE's
accuracy related to binnings in the dilepton mass. Model-independent fits to
$B\to K^\ast \mu \mu $ low recoil angular observables exhibit presently only
small sensitivity to different charm models. They give similar results as the
fits based on the OPE, and are in agreement with the standard model, but leave
also room for new physics. Measurements with resolution small enough to probe
charm resonances would be desirable.
