Well I'm back...
Dropped the NR off at my tech this morning and picked it up about an hour ago. (I took along my '04 for comparison purposes as well.)
First off, nothing awry with the wiring, untidy, but OK. While I was there, he desoldered the pickups and ran these individually straight into an amp and there was a dramatic difference (tone!). He measured the pots and these metered at a spit over 300K (they should have been 500K minimum), so it's no wonder the treble/presence was being sucked out of the bass. He's replaced all three pots and put a new cap in on the tone and problem is pretty much sorted. In closing, he also said it might be worth adjusting pickup heights next time I'm rehearsing.
I got home and ran the bass through my set up and the results were staggering; tonally it now shares a similar character to my '04, but hotter (which I can live with I guess!).
So there you are, hopefully problem solved! Woop!
Thanks for your input!
P