www.japarts.co.uk is one of them. They don't do all parts but, bits like balljoints and CV joints are in their inventory.
www.ignitioncoils.co.uk (I think that's the url) does OE ignition coils and amplifiers
You can get better that OE spec ignition leads (Magnecor spec), for around £25 from
www.ignitionleads.co.uk
That's just a few places.
As for them being 'pattern' parts, I'm not so sure. I bought a Blueprint waterpump not so long ago. It had the Nissan part number on it and a mark where it looked like they had ground something off it. On comparison with the waterpump I took off the car, the area that had been ground on the new pump, was where the Nissan emboss was on the old one ! Make of that what you will !