I guess there isn't really an answer for you. The larger / older the seedling, the more resilient they are likely to be. Your temperate range spread is potentially quite big. I'd guess that many seedling would be really happy with a night minimum in the high 50's, such that they were able to maintai...

#2 looks like a Trichocereus. These cacti may all be "hardy", in that cold and frost won't kill them. The combined cold and wet of a European winter almost certainly will. If you arrange very free draining soil, and a means of keeping them dry in the winter, they may possibly survive outsi...

That article is a good introduction but is quite out of date now.
LEDs have improved a lot since it was written.

#4 is not E. oxygona. It's a different Echinopsis, one of those formerly known as Lobivia, but I don't know which one.

It's Echinpsis oxygona, a common traditional windowsill cactus.

Different angles on number 4 and 7 would be helpful too, they aren't the most distinctive looking species.
4 may be a different Echinopsis (perhaps one of those formerly known as Lobivia) rather than E. oxygona.

I have the following seeds available for free: Aloe tomentosa (erratic but ultimately OK germination from July sowings) 1 PORTION ONLY Aloe microstigma (zero % germination from July and September sowings, see if you can do better!) 1 PORTION ONLY Aloe glauca (zero % germination from July and Septemb...

Aiko has several Frailea on offer for free (for postage from The Netherlands), see the most recent update to his post.
I got various seeds from Aiko a few weeks ago which are growing well.

Nice! Although, yeah, a bit early..
What size is the pot, to get an idea of how huge (or not) they are?

Its been warm, sunnny and dry for the last 10 days, so have kept watering.
Will get most of the plants in from the garden this weekend before rain forecast for Monday.
They may stay indoors for the winter unless we have another warm spell.

I'd thought about postal pollen exchange earlier, after I'd fertilized my 2 Ferocactus setispinus by storing pollen in the fridge, as they refused to synchronise their flowering.
It would be nice to get fruit / seeds on a few of couple of my other plants where I only have 1 specimem.

I see a need for an international pollen exchange service.

Where are you located? A lot of this depends on your local weather. So true. Here's a list of summer / winter growers http://davesgarden.com/community/forums/t/1046083/ I'd be wary of this, depending upon where you are and what species you are growing (e.g. Aloe is a huge genus of plants from varie...

Could well be T. peruvianus. Like people, they can vary a bit from individual to individual. Don't get hung up about minor differences in spine numbers and lengths. A decent sized cutting should be happy for weeks or even months if it's not kept somewhere baking hot. Let the cut end dry out for a co...

Echinopsis oxygona