That's the simple case for matching all six balls

Now add other prizes (UK: match 3, match 4, match 5, match 5 + bonus ball, match 6)

And work it out for multiple lines. The data is dependent on the other line; for example if I have "1, 2, 3, 4, 5, 6" as one choice, and "2, 3, 4, 5, 6, 7" as my other choice, I haven't greatly increased my overall chance of winning something, although my chance of the jackpot has doubled. Had the second line not included any of the numbers from the first line, I would have doubled my chance.

The answer involves a lot of permutations and combinations work (nPr and nCr), which in turn is a lot of dealing with factorials.

the bit I don't know how to do is to discount combinations that appear using both sets (2,3,4 is valid, and duplicated, but 1,3,7 is not valid)

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RatArsed