Moving magnetic lasso anchorage points

My question is can one move the anchorage poinnts after one has roughly selected the object and if so how do you do it.

No.

But you could try the Pen Tool (Freeform Pen option) with the "magnetic" box checked.

Move, no, but remove, yes.

With the Magnetic Lasso in use, click the "Subtract from selection" button in the Options bar, or hold down the Alt key. Either way, draw another selection that incluces the area you want to remove.