Posted: 26/05/2013 at 10:23
The spikes are to go into the ground either in soil or concreted in. You could still use them by drilling out appropriate holes in the breezeblocks then making up a fine grade concrete filling then fitting spikes in. I would be more tempted to cut them off and use screws and rawl plugs every foot or so. 2" screws will be fine. Regards to the door, is it on hinges? Or does it slide? If it slides does it not require the 'step' for it to be correctly supported and guided when closing? If it's hinged, then you will essentially be leaving that '2 ft portion' as a hole? What's your plan to keep it sealed?
The step is a pain granted, but if you have the space how about making a gradual ramp of maybe 3 or 4 foot up to the lip of the frame? It would be very gradual and there's no step and less headache than cutting the frame up! Also not sure what that will do to the stability, the greenhouse gets it's strength from the box frame at it's base, which you plan to compromise. Think very carefully before cutting the frame, there's no going back !!!!
Hope I've helped you have a few more thoughts. Oh, I have a dremel so I use that to cut aluminium. How ever I'm sure a fine toothed hacksaw blade would do as well. Wouldn't recommend a junior hacksaw, you'll be there for weeks! Good luck and let us know how you get on.