The simplest explanation I can give of the difference twix value based and principle based morality would be along the lines of this ...
A principle overides all other considerations. Thus a person who holds truthfulness, f'rinstance, to be a moral principle will be truthfull under all circumstances. The cost of being truthfull under any circumstance will not deter him/her. Such would constitute a principle based moral code.
Truthfullness can also be part of a value based moral code. The difference is that in a value based moral code the value of being truthful will be weighted against a scale of other values. The most common manifestation of that being the 'little white lie' wherein the value of telling the truth is weighted against considerations (not neccesarily selfish ones) of cost and/or harm.
As you rightly said "there are all sorts of values" and that is where the problem lies. Value sets, once the highly subjective and personal weighting of the value of this -v- the value of that begins, produces moral codes that are as numerous and as shifting as the sands.
In any case it seems that "principle" based folks may be a bit contemptuous of "value" based folks, and perhaps vice versa?
Strangely not so, I think ...
Principle based people (Gandhi, Mother Theresa, MLK, the buddha, et-similar, come to mind ...) tend to be extremely compassionate towards value based people often dedicating their whole lives to the betterment of life for them.
Equaly value based people seem to regard such principle based people, pretty much universaly, with the highest possible respect.
Where you do get contempt though is from value based people towards other value based people. That happens not because the core values they espouse are not virtualy identical. More so, that when the chips are down, any one persons weighting of one value against all the other values in any given moral quandry will rarely find a match.