The question of planning permission for a DIY or for that matter, any conservatory depends on a number of things. Firstly it depends on where in the country you live. If you live in what is known as 'designated' land, then your chances of even erecting a garden shed may be somewhat limited! Designated land includes areas like National Parks, The Norfolk Broads and surrounding areas, conservation areas, areas of outstanding natural beauty and World Heritage Sites.
Fortunately most of us don't live in these areas so the whole job is much easier. There are several basic rules to adhere to but for further information, contact your local authaurity planning department for advice, as the rules appear to change depending on the local council! Basically, a conservatory should not exceed three metres projection on an attached house, and no more than four meteres on a detatched house. There are also height restrictions in that the maximum eaves height of the conservatory must not be higher than the existing house eaves. Single storey conservatories must not exceed a ridge height of four meters. Check the web for your local council for the small print!