First, get yourself over to
http://www.pepipoo.com/ straight away. TONS of useful info over there. And from my (dodgy) memory the camera guys have a time limit to send you the letter, which you MAY be out of .... but I may be wrong, get over there and check it all out.
And on a positive note this 100mph = ban stuff is not 100% accurate. The courts still have discretion, as in my case. Caught at 101.2 in my car on the a3 (average speed over a measured distance) With 3 points already on my licence and a previous 28 day ban I was sure I was going to be off the road for a long spell. End result was 6 points and a 300 pound fine, which IMO had MUCH more affect on my driving speed than anything else would have (in the long term).
So there it is, find out where you stand. Ask advice at Pepipoo and be prepared to grovel in court, and best of luck.
P.S. On the insurance side, you don't need to mention it until convicted afaik.