Hello Ian,
If I may help, I sat for my Module 3 exams last year and managed a Pass. This was after several attempts and I was able to do so most significantly with PJW's help starting way back in 2007 and his comments through this website for which I am grateful.
The topics I attempted were all to do with Point and Signal/Route Control Tables and the Aspect Sequence Chart. As I am not from the UK but Singapore, I had to learn UK Network Rail practice which I must say was quite a challenge.
To facilitate this, I enrolled with Signet Solutions in Derby for the IST Control Tables and Signalling the Layout courses. So if you are like myself who is from a non-UK Network Rail environment, attending such a course would be a good starter. If you work for a company that has dealing with Network Rail try to get company sponsorship for at least the IST Control Tables course as some of my course mates were on company sponsorship.
Those courses gave me the necessary background for understanding but to prepare for the exams much more was needed in terms of additional notes that are now freely available on this website and practice, practice and more practice of past year exam papers under close to actual exam conditions (with time limits) for which PJW will readily give comments. From this website, you will have a good feel as to the number of past exam papers I attempted in preparation for last year's exams. You will also find that too help with very real exam-related issues like the format of the Control Tables which I find the Network Rail ones time consuming to draw under exam conditions.
If you intend to attempt the same questions as I did, I can tell you that the Module 3 Study Pack from the IRSE does not have any information on Control Tables or Aspect Sequence Charts. On this website for Module 3 you will find the following very helpful and you may want to download and study them in the following sequence:
1
Control Tables PJW.doc which covers Control Tables and Principles
2
Bite-sized Revision Notes. Although intended for quick revision for the exams, these notes will help to cover the gaps not covered by (1).
3 Appendix S of the Module 2 Study Pack which is very good for the preparation of the Aspect Sequence Charts. [A draft version of this was posted on the website (in several portions since so large due to inclusion of ascanned examples); I have since removed it when the Study Pack was produced. It has been completed for the 2009 edition as art of the DVD that all exam registrants should receive. I therefore don't propose uploading here again, but if anyone paricularly wants a copy then email me. PJW]
Personally I found OS Nock's book difficult to comprehend. Maybe it could be because I tried starting off from there without any basic understanding but you may find it otherwise.
If I may be of any other help please let me know.