I’ve used “Vehicle Wiring Products” a few times. No complaints and a good variety of stock. Have some odds and sods specific to cars, and to bike too.
www.vehicleproducts.co.ukThey’ve a handy little catalogue they'll send through if you bell them 0115 9305454.
Myself and mate Andy use their braided plastic sleeving as a way of making bits of visible wiring loom look rather neat on bikes following a tip from a retired RAE engineer who’s restored countless British vintage bikes.