All timers I've come across so far (like this) are designed to to turn the appliance on/off at regular pre-configured intervals on specific day(s) of week.
What I need though is a simple count-down style 240V digital timer with on/off button, that would allow to me to set an interval once (e.g., to 15 mins), then hit the On button and leave it to let the connected applicance run for the 15 mins
Any suggestions/links are greatly appreciated, thanks!
I have seen bathroom heater lamp which you turned on by hitting a button and it will switch off automatically. However, for high powered application, you probably need to get it installed by a sparkie. Check your local bunnings.