After reading your post again, with a bit more attention this time, I notice you say one wall will form the boundary of your property. It would then fall under party wall legislation and may be a problem to build without special planning permission. I take it you do have planning permission already for your proposed original site ? If not, stop even thinking about building anything until you do.
A conservatory falls into two categories. Firstly you have what is refereed to as a glue on conservatory, which is just a glass covered patio area. It consists of a small foundation which takes the weight of the people walking on it, rather than the actual structural weight of the whole build. A glued on covered patio needs written consent of non-objection from neighbours who will be looking at the thing when they go into their own property, and is also regulated by drainage warrants for surface water soak away.
The second type of conservatory is totally different. This type of conservatory is called an added room to your existing property. Now adding a room to your property, as you can imagine, brings with it all sorts of regulation and legislation for ground support (foundations), structural height (the roofing material) and wall spanning (the size, shape and weight of the whole thing), all of which must be drawn on paper and submitted to your local planning department for approval. The local planning and building control people will inspect the site for any drainage problems, overlooked area problems (this is in case you have any pervs' about, remember the see through walls) and any conservation notices on the land Etc, Etc.
Now you say you'd like to use the area as an actual dining "ROOM", and I emphasise "room", and therefore, you need to plan for fire break qualities, escape route plans, thermal regulation properties, floor structure design (remember, if it collapses while you have guest in it, it is a manslaughter charge) and insurance restriction for its security qualities.
So, after finding out in more detail what is actually involved, do you still plan to bang posts into the ground to take a few panes of glass and lay a couple of pallets on the ground with a plywood sheet over them ? My advice to you is, "you should now go to an actual company that does them for a living, and ask how they go about building one of these things". Put your mind at ease.