Kat, I think you are misunderstanding somewhat. Of course, it does effect our credit rating to not be on the electoral roll, but it's just a part of it. I am not on the electoral roll, but I have a mortgage, credit card, and car loan in my name and an excellent credit rating.
You say you have an excellent credit rating, but you don't. You will have a pitiful one. That's the nature of starting in a new country. You won't have a credit rating since you haven't built any credit whatsoever. To do that you'll need things to start out. If you have steady income, your bank will usually work with you. That's where I started out. Once they saw I had monthly solid income, they were happy to give me an overdraft and a credit card with my bank account. That's where I started. Others have started with the riskier credit cards, and you can get them without being on the electoral roll. It's just one of the parts of your credit check that determines eligibility.
As for the notice of correction, many of the others are right, you don't file it with the electoral roll. They can't do anything for you. You file it directly with the credit reporting agencies, of which there are three major ones (and other minor ones). Some of them won't just take it from an email or something. I had one that I was able to send a letter in the post to with a notice of correction, but the others I had to actually get a copy of my credit report and THEN file a notice of correction that something in the report they sent me wasn't sufficient. I don't think sending an email would cut it, and even if it did, they take their sweet time getting back to you and it will be a bit before it shows up in searches.
The nice thing about that search is that if there's a notice of correction, a real person has to handle your search, so it takes it out of the realm of an automatic computer refusal based solely on numbers and you have a higher chance of them being reasonable, but like others have said, you're probably going to have to start with the higher risk credit things at first to build up some actual credit history, just having a bank account just won't cut it.