NOC insurance

... agreed value as it's a big risk getting classic insurance without. They'll just tell you the market value of your bike is £100 should you be unfortunate enough to lose it.

I have also been hearing that many modern bike owners are insuring their modern bikes for less than £100.00 as well, which doesn't seem right. 

I dealt with many motor insurers in the years that I worked in crash repairs. Cheap insurance is just that- cheap- often barely worth the paper its written on. I could give you many horror stories on that count.
I'm sure you've had several quotes: if most are around the same price (for similar cover that is) but one is significantly lower, I would look very carefully at it before signing up. Small print, exclusions etc, and of course Reviews (but take internet comments with a suitably large dose of salt.
That said, 60 quid to insure anything seems too good to be true. And you know what they say about that.