My home page is split in two with the main body of the forum and at the side the widgets, no problem there.

Is it possible that when a user goes onto a category the page would could be one full width page, ie no widgets?

If so how?

Try this links;
https://help.forumotion.com/t8322-differences-between-forum-and-category
https://help.forumotion.com/t3313-categories-and-forums-creation-and-appearance