Hi Olly, Your stock probably has a synthetic varnish on it. This means that adding oils to it probably won't work. Why not just polish it with wax furniture polish ? I have used CCL Gunstock conditioning oil on a Matt Beretta stock, with limited success. I rubbed it in very sparingly, and waited a long time for it to dry, as it doesn't sink in. Furniture wax is probably the best way to go, unless you want to strip the varnish, and start again.
Marcher.