I'm building the base for another "Steve" greenhouse this week - with a couple of differences. My customer has asked me to make the porch a little longer - 1m out rather than 0.5m - and to add a cold frame on either side.
The site is between two tall beech hedges. You might assume is would be too shaded here but not at all - I was working in sun all day. This was the location of an aluminium greenhouse which performed very well for many years so they know what they are talking about!