Stellar metallicity from optical and UV spectral indices: test case for WEAVE-StePS by Ditrani, FR, Longhetti, M, La Barbera, F, Iovino, A, Costantin, L, Zibetti, S, Gallazzi, A, Fossati, M, Angthopo, J, Ascasibar, Y, Poggianti, B, Sánchez-Blázquez, P, Balcells, M, Bianconi, M, Bolzonella, M, Cassarà, LP, Cucciati, O, Dalton, GB, Jin, S, Spiniello, C