I would stronly reccomend against "oil" based lubricants. I cant speak for the others who have indicated that they use them, but I have find it to create some bad reactions.
I use this stuff;
http://www.chicagoairbrushsupply.com/suluailu.html
Last time I bought a tube of it was close to three years ago and I still have close to 2/3's of a tube left. It is safe to use for solvent based and acrylic based paints. Picking it up in the
UK should be no problem either.
Ashton