  We present an update on ongoing work to extract pseudoscalar and vector decay
constants for $B^{(*)}$, $B^{(*)}_s$ and $B^{(*)}_c$ mesons and determine
phenomenologically-interesting ratios such as $f_{B_s}/f_B$ or $f_{B^*}/f_B$.
Our calculation is based on ${\rm N_f}=2+1$ dynamical flavour gauge field
ensembles generated by the RBC/UKQCD collaborations using domain-wall fermions
and the Iwasaki gauge action. Using domain-wall light, strange, and charm
quarks and relativistic $b$ quarks, we obtain results at multiple lattice
spacings and valence quark masses.
