The ornamental design for a fold-up workshop, as shown and described.
FIG. 1 is a top, front, and side perspective view showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a top plan view thereof; and,
FIG. 4 is a right side elevational view thereof, the left side being a mirror image of that shown.
Throughout the various figures of the drawings, certain views are not provided. The omission of a particular view is intended is convey that the elements depicted is/are plain and unornamented in that omitted view, or that the particular ornamental appearance in that view is simply not claimed. Where included, broken lines showing environment or structure are for illustrative purposes only and form no part of the claimed design.