Could you have the door on the back on the ladder, like this:

Where's his helmet and safety harness?

Windscreen wiper motor.

Indeed, for a man who stores his dustpan upright on a shelf, he should know better... he'll have a boiler suit set aside for DIY matters, a utility belt/kilt for demanding jobs and his screws all sorted into individual compartments in a wall thinger.

And just run it for x seconds?

It is a nice idea, but I think they're still too expensive, pretty tight budget.

Mine are piled in cardboard cartons -- when I remember to put them back.

Or I could use a hall effect sensor or two to detect whether it is open or shut.

Mine are in an old Fairy tub. :J

They use a mechanical linkage which reverses direction (motor runs continuously in one direction), so just install it so that turn in direction coincides with the max open position of the hatch, then add a limit switch to stop the motor when it reaches there.

They use a worm gear in the gearbox so produce substantial torque, but I've no idea if it's enough to lift a MDF door from horizontal. If there was torque figure available somewhere it's fairly trivial to work it out, though. Or just try it and see, if I doesn't work you have a spare motor for making a robot.

Is it finished?

Which bit?

It's half boarded and the hatch frame is in. Should get it pretty much finished tomorrow. Then I'll design some ridiculous way to open the hatch door.

What about having a piece of hanging 'art' on the wall beside where the hatch is?

Use it as a counterweight, if you want to open the hatch then just give it a gentle tug downwards and marvel at your secret entrance skills :D

My dad has suggested a counter-weight method too, with the weight in the attic.

It would still require the door to be pushed (at least initially), but it would make it much easier.

We've also realised that with a top opening door it may need some space for the loft ladders, unless the door actually goes within the frame rather than on top. Anyway, I've got enough MDF left over to sort that.

Spring(s)?

Have you got any pictures of what you've done so far?

Whenever anyone's telling me about their DIY projects my mind automatically imagines an Ikea-like paradise where everything fits neatly, walls are perfectly straight, you've got all the right screws to hand and there's never a dead battery, all in a room lit by white light coming through diaphanous curtains. I don't know why, 'cos my own DIY projects are usually messy affairs covered in filler, caulk, paint, blood and much swearing.

My DIY project sounds very similar to yours. I've taken a few photos of the hatch progress, I'll put them up later. I'll take a photo of the finished flooring once it's done. I was going to put a camera up there and timelapse it, but it's so so filthy.

My dust mask from yesterday

Filth. :C

But I would like to see how it's going - always interested in DIY stuffs.

Glad to see you have the keys to the windows, in their rightful place, on the window sill.

And the getaway car parked nearby.