coldframe/cloche/fleece/plastic?

I do not have a greenhouse and have environmesh covers over my blue piping raised beds which works sort of but has collapsed over my brussels and Kale. I want to extend my growing season and grow earlier and later but am getting lost in the gardening books. Mainly I would like to sow seeds earlier and have crops sooner in the spring. Should I buy a coldframe (if so any recommendations), or go for cloches (again recommendations) or just buy plastic or fleece to go over my blue piping, which works up to 1.5 ft but doesnt like heights and falls over. My vegetable beds are 100ft from the house over wet clayey glass, so cant see to cloches every day before going to work). On a budget, however dont mind investing in a coldframe if will last years and get good use out of it but have read on web they blow away in the wind so want to make sure I get right one Any help would be appreciated
thanks
Alison