I would personally dig 600 x 600 with a 250mm thick concrete footing to carry the dwarf walls and the conservatory. I would never comprimise cost to long gevity the foundations are the itegrity of your build.This asumption is that there are no nearby trees and your not building over drains. Good luck with your project
Regards Ken

Your depth of footing is 1000mm deep from dpc. If you are excavating these mechanically, a 450mm wide footing that is filled to the top with concrete (trench fill foundation) is more cost effective than building from a 225mm concrete footing with all the labour and trench blocks and it saves you time. Julian

you would need to dig down to 900mm, a bit moore if the ground is soft,regards Terry.

You only need a footing thats around 600mm as there is not a lot of weight in a conservatory unlike with an extention it would usually be 1200mm to 1800mm

did down 1mtr from dpc,
if ground still soft keep digging
you will be surprised the amount of conservatories that get subsidence.
because they dont do it right first time.
steve

Hi
first of all a wall of 2050 high no longer makes your conservatory a conservatory but an extension, standard dig for footings is 1000 deep and 600 wide, and then get the building inspector in to check the trenches are fine and you can concrete, i know it seems on the deep side but this is the part that matters. ( also check what you are building a conservatory or an extension as a extension requires plannning and only sometimes conservatorys need planning) if in dout still as there are many different answers here contact your local building control they may help you.
best of luck
Tom