Posted: 03/03/2017 at 13:25
First thing to think about is water. Have a source of water close to the greenhouse, either piped in with one if the plastic irrigation systems or at least have a water butt beside it which you can top up with a hose, you don't want to be traipsing up and down the garden with watering cans if you can avoid it.
What veg are you planning to grow? Plenty of us started with tomatoes but stick with what you enjoy best. You can get early crops of strawberries in containers, salad leaves, chillies, herbs which like heat such as basil, lots of possibilities.