When to move from indoors to the greenhouse?

I have a lot of young plants stacking up on the conservatory windowsill and am wondering when to start putting some into the unheated greenhouse on the plot. This is the first time for growing from seed and also I've never had a greenhouse before so I'm new on both accounts!

I've got some cucumbers (F1 Burpless) that are around 5" tall and some San Marzano tomatoes at around 4" tall which I think might be ready for the greenhouse. I took some of the cucumbers down to the greenhouse today thinking to make space at home but it was hot in the greenhouse even with the door and window open and they started to wilt! I took them back home and they perked up again.

These plants have lived a privileged life so far, warm, out of direct sunlight for most of the day and no drafts/wind.

So my questions are...
1) With such big temperature changes at the moment (day and night) am I best to hang on and let them get a bit bigger before I move them to the greenhouse?
2) Do I need to harden them off in anyway, considering that they will stay in the greenhouse?

Maybe you could let me know what you do and what works best for you?

OK, thanks Peter, that is good info but did you mean planting outside? The plants I mentioned are destined to stay in the greenhouse and to grow there.

Thanks Peapod, one of my worries was the daytime heat in the greenhouse in this sunny period was making the cucumbers wilt, or is that just part of the hardening process the plant needs to get used to?

heh heh - I'm not a cucumber fan either, I like them but they don't like me (if you know what I mean) but the kids love them.

The plants were fine on the windowsill but the leaves drooped in the greenhouse heat, you know the feeling you get when you suddenly walk into a really hot room, that is what the cucumber plants must have felt. I don't have the experience or confidence to just leave them in the GH in case I'm doing it wrong so I took them home again and they are now all pert again The compost felt moist but not 'wet'.

Very good point, it is tinder dry so I'll up the humidity tomorrow. Thanks for your suggestions.

Thanks Peapod, one of my worries was the daytime heat in the greenhouse in this sunny period was making the cucumbers wilt, or is that just part of the hardening process the plant needs to get used to?

If you have no shading then they might wilt even if well watered... try laying newspaper (one sheet) across them to protect them until the foliage has toughened up. I do this with anyhting I move from the windowsill to the greenhouse for a few days as it stops them scorching. (Got the shading up now though  )

Whitewash can be hard to clean off in the autumn. A lot of people on our site just fling some debris netting over. I staple old compost bags to the frame to shade out the worst of the sun and put stuff under the shelves as well. It's already been over 30deg in there. In a few weeks I'll have to take everything out.
Cold frames can be useful then because you can leave them open all the time and they just act as a windbreak until things have hardened off.