I won't sell mine, but I much prefer it to the Serek, which is nice too. When I bought the Wilcock the bass was pretty unknown (I think I posted about it here) and I got a good deal on a Mullarkey made for me. I found the build quality and tone superior to Serek, but the Serek I played felt more like a rocker's short scale bass and the Mullarkey screams R&B/Funk/Deep house/Jazz fusion. The best way to explain it, is that it is a deeper, richer P Bass. I just did a session yesterday and recorded both (both have flats btw). The P Bass has that classic woody sound we all know, but the interesting part is the closest I can get to it on the Mullarkey is the back pickup. That's how insanely deep the bass sounds. The back pickup is probably my favorite of all time for getting that clarity plus rich depth. The front pickup is just a monster so if you play Reggae/R&B style and want a giant huge thud - it is the king there.
Its just a fantastic bass and I am really glad I got mine before they got more popular, as I imagine the wait times are pretty long now with more and more famous bassists using them.
So yeah, if you like really deep sounds and notes that still have good definition and a nice sophistication to them - go Mullarkey. If you are more of a rocker who likes to turn up the grind a bit, I think the Serek makes more sense.