hanging basket advice

Hello all,
I'm branching out from my usual vegetable growing this year and have bought some flower seeds and plants.
I have bought some baby plug plants, lobelia and others that I intend to use in hanging baskets. I'm not quite sure what to do with them now as it's too cold to put them outside, planted up. Should I leave them in their tiny plugs or plant them up into bigger pots until it's time for them to go in the basket? Do you think they will be OK outside under the plastic of my mini greenhouse or is it best to keep them indoors for a few weeks?

Many thanks!

the frat free greenhouse.

No unruly teen-agers in your greenhouse then?