Hello cloud8,
I am a cold frame fan, I have had amazing results from both of mine, I've grown loads from seed. For me it's cold frames all the way.
From what you say that you want to grow,you can do this in a coldframe, and at a very low cost and they don't take up much space and very little maintenance
.This is one of mine in Feb this year. It's been moved recently to make room for a potting shed.
Currently it has trays of perennials & biennuals grown from seed ready for next year. The other one has plenty of room for overwintering plants