Forgot to add, I tied a small loop of rope around the handle of the velux window to latch onto when I am reaching up with the boathook. A quick tug allows me to open the vent, or open the window fully. Pushing on the boathook closes the window.
It doesn't look pretty, but my window is up a tunnel in the flat ceilinged hallway, so it's not obvious. No doubt a better looking loop of something could be found, if that's the road they go down.
When we got velux installed we opted for the motorised versions for some of the windows... they are extremely handy and mean that we open / close them more often than if we had to do it manually versus remote control. The one in the kitchen is directly over the cooker so is an excellent extractor fan. I am aware op stated that not an option currently due to cost but perhaps consider installing wiring now for future upgrade.