That looks like an 'ultraframe' roof, to confirm the coffin shaped end caps on the end of each rafter should have like a 5 leaf clover/flower design.
If so slide these caps up and off, you expose the aluminium under rafter and top cap cross sections, the 2 vertical prongs in the center of the top cap need compressing together with 2 flat bladed screwdrivers at the same time as pulling the cap up, can be tricky but they will peel up, I can do these in my sleep. The caps hold the sheets down onto the rafter along with a strip of glazing tape along the bottom between each rafter, from inside run a stanley knife between each rafter against the poly carb sheet cutting through the tape, it's just a 3 or 4mm black sponge tape, sometimes can be white. Once cut the sheet should be loose, from outside lift the sheet up and yank it down, the sheet locates into a groove along the top but will pull out, carefully not to fall back off the ladder.
At the end of each rafter top and bottom you should see some 10mm nuts, these hold the rafters down to the ring beam, that's the heavy aluminium lintel type thing that runs the circumference of the conservatory, remove these in a sequence that suits you and your helpers. The ring beam is either screwed down into the frames or upwards through the frames into the beam, opening the top sashes should expose screws if screwed upwards, remove these. You also have a box gutter, these are heavy and rest on the frames at each end and also bolted through into the house timber rafters, can be a pain to find and remove the fixings.
Next you'll ask how do you remove the gutter from the brackets I just know!
