LeeThorogood said:

Unfortunately I can't afford the equipment needed to capture the Dolby Digital audio track, so I will be capturing the stereo track instead. I don't have a surround sound system so I wouldn't get the benefit of 5.1 surround any way.

The PAL laserdiscs don't have an AC3 audio track.

Any advice on which input to use (Composite vs S-Video),

Test both, and use the one that gives the best picture quality.

best practice for capturing with my set-up and any recommended filters / effects in FCP would be a massive help!

Sorry I can't help with the Mac side of things.