Planting Out Forced Hydrangea Macrophlla ?

I have been wanting to get some Hydrangea Macrophlla and spotted some for sale at £5 a plant which was cheap. However its March and these pants were in full leaf and bloom...clearly greenhouse froced. I could not resist and got 3 !!! My question is will I be able to plant these out in my large wooden planters ? When I got them home I cut off all the blooms re-potted them into larger pots and placed them into a warm south facing geenhouse for planting out later in the spring ??? I have read that "florist hydrangea" are not the same as nursery sold types ??? Has anyone ever done this ? I live in Zone 8

It can be hardened off for a couple of weeks and then planted outside after the last frosts. Many florists hydrangeas are dwarf, of a variety called 'Pia' and willl not grow past two feet tall, but you won't know until you try. That can be quite handy in a trough or pot. They don't like full sun or too much morning sun and they are supposed to like plenty of water without being waterlogged. Having said that, I have lots in pots and they aren't watered as much as they should be, yet they do fine.

There are many different hydrangeas but most macrophylla do well in zone 8.

Thanks well I did have them out last week but brought them back in due to the bad weather 

http://www.gardeningzone.org/content/content.php/hardiness-zones-uk/ 

But weather  this still applies now we're having an Actic Blast I'm not sure (joke - I think)