Some people are
way out of date re. Oceanic procedures and others are simply
wrong!
C152R (and others) I suggest you:
Follow this link to
ICAO Doc4444 Amendment 2 and see
15.2 "Special Procedures for in-flight contingencies in Oceanic airspace" Also suggest you look at
16.5 "Strategic lateral offset procedures (SLOP)"
Follow this link to
CAA CAP694 and see
Chapter 9 "Special Procedures - Shanwick Oceanic Control Area (North Atlantic Region - NAT)"
Follow this link to
NAT Regional Supplementary Procedures (SUPPS) (Doc7030) which should provide answers to more general questions.
Come back if you're unsure of anything, having read the above, as I may be able to help.
RK
(EGGX ATCO)