[quote name='brensabre79' timestamp='1445880772' post='2895014']
A good place to start, and a cheap solution if it works, is to add a small shim to the front of the neck pocket. A business card or similar should do it.
I'm guessing at the moment the curve is up and the top of the neck, so a shim will flatten that out, so you might need less truss rod compensation then too - which would make the action more playable.
[/quote]
I've given that a go, and it makes it a bit more playable, but action upwords of the 7th fret was terrible.
I think I might end up trying one of these... http://www.ebay.co.uk/itm/BRAND-NEW-20-FRET-ELECTRIC-BASS-NECK-SKUNK-STRIPE-J-MODEL-MAPLE-ROSE-FB-/231671994275