Wishbone rear bush debonding

My Superb 2.0 SE business tdi estate just passed its MoT with the following advisory:

Offside front suspension wishbone rear bush debonding.

Before the MoT I replaced the tyre which had heavy wear on the inside edge.

Would I be better replacing the bush or the wishbone complete? People also talk about replacing the steel ones with alloy from an Audi. It this worthwhile for one side only? In which case what it the part number? The car is now pushing eleven years old with 86,000 on the clock. It is our workhorse.