You need to prepare a solid base which has 2 earth beds, 1 each side of a middle path. Position the door facing south with 2 vents on the west side and one on the east side. Metal is more durable than wood, coolglaze can be painted on the inside in the summer months. The best company I have used for a greenhouse is Eden, if you Google them they have a wide choice which you should find suitable for your needs.

Buy the very best you can afford is the only advice I can offer!

I would modify Ian's comment by saying buy the largest greenhouse that you can afford/fit in (it will still be too small in a couple of years) but also the cheapest in aluminium and glass. You can always add an extra ventillator or two or, as we do, remove a pane of glass in summer.

Oh, I do agree with Mr MB! I bought a greenhouse as the first thing we did when we moved here 5 years ago - it was soon far too small. Think BIG...

I have automatic vents in the roof, indispensible, and vents at the end as well. If you can run an electric cable out there, that will open up a much broader range of activity, as well - for an electric propagator and a fan heater. I use this for cooling in the summer and heating in the winter.

My two are Hall's, and they're fine. I got them direct from Halls, as they offered the best price.

the very best tip i can give is never ever never buy a greenhouse with polycarbonate windows ,i did it was the worst investment i ever made .it fell to pieces the wind blew the panels in its now stuck together with duck tape ,,soon to be skipped

I agree with you all THINK BIG I've got an 8x10 and I've been very pleased with it, I would advise you put a concrete base for the frame to sit on and through the middle were you walk it makes life so much easier and cleaner. We brought a Halls one with 2 Automatic vents and one at the end, I also have electrics fitted in there.
Good Luck .....

:-)))