Need Some Help Planning My 2015 Outdoor Grow :)

Hi all, I'm currently planning my outdoor grow for the 2015 season

I'm planning to buy the Dutch Passion Colour Mix #1 pack: http://www.dutch-passion.nl/en/cannabis-seeds/product/colour-mix-1/

This contains the following seeds:
2 x Frisian Dew
2 x Passion #1
2 x Shaman

I was originally planning on growing these just in my back garden, outside, but realised that I could grow them in my greenhouse instead. What would be the pros and cons of each option? I could always do say 3 in the greenhouse and 3 in the garden if one of the strains is better off in a particular environment. Also, how big do you think these girls are going to get? As in would I be able to fit three or maybe 6 in my greenhouse, considering its about 3 meters long, 2 meters wide and 2.5 meters high.

I am planning to use the following nutrients for my grow (all organic):
BioBizz Bio-Grow: http://www.biobizz.com/products/organic-fertilizers/bio-grow
BioBizz Gio-Bloom: http://www.biobizz.com/products/organic-fertilizers/bio-bloom
BioBizz Top-Max: http://www.biobizz.com/products/organic-stimulants/top-max

I have yet to buy my soil (I'm planning to grow these in post, unless you guys suggest otherwise), I was thinking about getting the BioBizz All-Mix or Light-Mix, do you guys recommend any particular brand of soil, bearing in mind what nutrients I'm using etc.
http://www.biobizz.com/products/organic-substrates/all-mix
http://www.biobizz.com/products/organic-substrates/light-mix

What do you guys think of my plan? I'd love any suggestions/improvements from growers experienced with growing outdoors/in a greenhouse in the UK.
I've only grown one plant before, an auto flower that went ok I guess considering it was very poorly treated, I've learned a lottttt since then

I've also just finished reading a grow book, its called Medical Marijuana / Cannabis Cultivation: Trees of Life at the University of London So I've picked up a lot of information from that, and recommend it to everyone!
Heres a link to the book: http://www.amazon.co.uk/Medical-Marijuana-Cannabis-Cultivation-University/dp/0955011221/ref=sr_1_4?s=books&ie=UTF8&qid=1422299166&sr=1-4&keywords=medical+marijuana

Thanks!

P.S My Latitude is 51.9 if that helps..

@doublejj carport for this fella ??^^^^

Greenhouse is nice, cause it's warmer and keeps the rain off. It also keeps the wet air in, unless you have good ventilation. Greenhouses also get hot under summer sun, again back to ventilation. Are those seeds fem? If not then count on males.Are they going into pots? A 20gallon is about the max that I would want to move around, but you could plan on trying for the best of both worlds if you can move them. You are a bit north of me, so I would assume a shorter season, this is your crucial detail. Even if you can finish in a dry greenhouse, there most likely won't be enough intense sun to finish a longer strain properly. When do the cloudy cool, rainy days start consistently happening?

how big is t
he greenhouse.

I'd say being in the UK your best bet is in the greenhouse properly set up ventilation. You'd be able to get 6 nice plants in that space, top em a few times to get nice bushes. Start putting neem granules in the soil now if you're growing in open ground? It'll help condition the soil and keep soil borne pests away.

Put any auto flower strains outside in the warmest 3 months of the year.

Good luck bro, wish I was in a position to grow in a greenhouse.