Mummy-
The wiring diagrams for your coach are
here. According to the Front End Wiring Installation diagram (link
here), Sheet 2, Zone G-6, the driver's power seat fuse for a Workhorse is a 30A fuse on a block located under the flip-up dash. I've attached a snippet of that diagram with the fuse circled in red.
Page 9-7 of the operator's manual for your coach (link
here) shows where to find the fuse block under the flip-up dash.
[EDIT]I see you beat be to it by 16 minutes. Glad you found the fuse.[/EDIT]