Yep, FM isn't CD quality but worth trying for only a few pounds. I'd go with one that uses an Aux cable so you get the best quality from the phone to the transmitter. If you use a bluetooth one, you have the wire-free connivence but you lose quality on the bluetooth connection from phone to transmitter and then from the transmitter to FM.
Actually, as you have an LS430, and I assume a tape deck, you could use a tape adapter instead to avoid the FM reception issue and possibly better quality too.
http://www.halfords.com/technology/mobile-phone-accessories/audio-accessories/belkin-cassette-adapter