You're most welcome PappaG.
Your questions are answered inline. :)
1> If the restore fails for whatever reason will I still be able to use the existing system prior to the restore?
Usually when a image recovery fails, it reverts back to the prior installation automatically.
2> Is there a chance I will end up with nothing if the restore fails part way through for example?
There's always a chance of say a power outage or somthing that may cause it to fail. If the system image is good, then you could just start the recovery over again. If the system image is not good and it didn't automatically revert to the prior installation, then you may need to do a clean reinstall.
3> Can I move the backup root folder to another larger HDD putting it in the root of the HDD and then restore from there?
I have not tried that, so I can't say for sure. If it doesn't work, then it should be able to by moving it back to the original location.
4> Can I put a new larger HDD in my system to take the O/S, i.e. a New C: drive (formatted NTFS and pinned as Master) and restore the backup to this new HDD? from by backup HDD (seperate disk).
Yes, you sure can. However, you will have unallocated space left over on the new larger drive for the size difference between what the image of the older drive was for and the new larger drive.