With my car came a set of locking wheel bolts, but they have the wrong shoulder, they don't fit snug into the wheel like the other bolts do. I want to fit some 5mm rear spacers but need 5mm longer bolts and ideally another set of lockers that fit properly but dunno where to get them from.

Does anyone know of the technical details of the bolts etc?

Try mcguard wheel locking nuts had these on my last car, they are pretty good.

i dunno the bolt spec though :-\

Anyone?

M14 x 1.5 I think can't remember if they are radial or conical seat though.

I would imagine yours will now be tapered seat (standard are radius) and as said standard bolts are M14 x 1.5 x 30mm.

5mm rear spacers will obviously not be hub centric but as the mounting is quite deep anyway you should be ok. You would need 35mm long bolts, you are ok going longer on the back as there is room behind the disc but on the front you can't as the bolt will bottom out on the bearing carrier before tight.

I got some tapered bolts off eBay, they were 40mm long and I cut 10mm off them.