No worries and thank you for your response. After doing a bit more tinkering and trying the bass through a better rig, I am more impressed with the Warman. The bass response from the E is a bit better now I have lowered the pickup a bit and is more balanced in comparison with the A and D, which were dominant previously. There is also more of a distinct difference between the parallel/single coil/series modes. The series is distinctly louder and darker than parallel now, which is more what I was expecting. Parallel sounds much more 'Ray like, although given the central position of the pickup on the Jag, it is never going to be totally authentic. The big revelation is the single coil position (neck coil) which reminds me of a '51 Precision pickup (SD 1/4 pounder) I have in another bass. This wiring and the Warman certainly gives the Jag a few more tonal options. For around £25 (this side of the pond) you get a lot for your money.
I am sure you are right about trying different strings. I still have the OEM strings that came on the Squier (whatever they are). They are not bad but I am sure I can do better with a more recognised brand, although the options are somewhat limited, as the Jag is medium scale.