@Malcolm- Thanks for that information. That sounds very good indeed. One of the OPR marriage certificates I purchased was for Dunfermline. I could have saved myself a bit of cash there. I'll no doubt have other relatives in Fifa so that's good to know and I will look into an equivilant for the old Lanark area.
@DavidWW- Thanks very much for that insight. It would appear my knowledge of the process was not as clear but as I thought. I can see what you mean about the difficulty in obtaining the correct entry. Maybe I've been a bit spoiled with online images at SP and would love to see a similar setup for the OPR records with the same pricing structure. When it comes down to it though I have about 8 or 9 entries to acquire at the moment and £80-90 is just not affordable for what I would get in return. Thankfully though plenty of cheaper alternatives have been posted.
DIGROS is great but as you pointed out is limited to the years on SP. I never knew that before going to New Register house. I had taken money with me that I didn't need but I did need my pad and pen. It was well worth it though despite the sore wrist.
Thanks again to everybody who has posted.