You are right
Point being they want someone to do an hour here, an hour there. Not 1 full day/2 half days etc, which would imo be perfectly acceptable.
Are you on a wind up or are you being serious? We've never had an Arts technician before now so its obvious we dont
need one. Besides, are you comparing my skill set (CCNA, server2k3, *nix, web design, A/V, etc) to that of a guy who orders paints? The school is hardly going to grind to a halt if they are missing the tartan paint, but it will if the network went down.
Personally i think its not a bad job for, as FN-Greatermanchester said, a little old lady who lives round the corner who just wants something to do in her spare time, but if i was HT i would feel ashamed of myself if i made her come in for silly hours for £50pw*, thats where the problem lies for me; "flexible hours". You'd have a hard task holding up another job if they kept asking you to come in every other day for an hour or 2s work.
*i based the figure on payed weekly over the course of a year.