Why does Victor want to visit England? What do you make of his talk of slavery?

In essence, Victor wanted to visit England in order to get scientific advice.

I remembered also the necessity imposed upon me of either journeying to England or entering into a long correspondence with those philosophers of that country whose knowledge and discoveries were of indispensable use to me in my present undertaking.

Victor likened the task of creating the creature's companion to an act of slavery.

My promise fulfilled, the monster would depart forever. Or (so my fond fancy imaged) some accident might meanwhile occur to destroy him and put an end to my slavery forever.