Onion Sets and Garlic

I just got my onion sets and garlic over the weekend.  Half will be going into the polytunnel and the rest into a raised bed on the plot, when is the best time to plant them.

I think Garlic planting time depends on variety - dunno how to tell which varieties / when, as it isn't a simple rule for Hardneck vs. Softneck, other than looking them up ...

Here's a chart (but only of the varieties that they sell):
http://www.thegarlicfarm.co.uk/when_to_plant_and_harvest_garlic_uk.aspx

those listed for spring planting are also in the list for autumn planting.

Hadn't spotted that, thanks   I'm still confused though as I read here-and-there that some varieties should be delayed and planted later (December/January). Maybe its just "Ask two gardeners and get three opinions" though?

Personally I'm not in too much of a rush as a) I'm never organised enough to be on time! and b) if we get a very warm Autumn it may promote more green growth before winter than I am happy with.

Put another way: are there any good reasons to delay planting until, say, December?

Thanks folks, I have the outdoor bed all nicely dug over and rotovated so hoping to get them in on Tuesday.  I cleared the courgettes out of the PT bed yesterday so I should have it ready next week.  They are winter sets, but I am only doing two small lots this year to fill the gap, my seed grown onions were so much better this year I have decided to concentrate on them instead.

OK, so you might see a few maybe 3 months or so later than they should be out, but not 6 months! Knowing how carefully some keep their stock, any they might have will have turned to dust & fallen out of the netting/holes in the bag!