Building verandas takes an awful amount of planning there are many different elements that need to be taken into consideration.
Below are an outline and then some finer detail of those items:

Positioning - Where about on your property is best to place your veranda?
There are many different areas of your home where a veranda will fit with best possible effect, for instance. The patio area probably the most common area of all and in many opinions the best place of your home. The front entrance (front door), depending on the size of your home a veranda could take place of the common porch as an alternative, who says you need to sit at the back of your house to enjoy your garden? Verandas can also be built onto the sides of houses to form another sitting relaxing area and also double to form a carport.

Planning permission - a few guides on planning permission.
Planning permission and building regulation can change from council to council but in most cases an area not exceeding 30sq meters is exempt from planning. Also a veranda or porch not exceeding 3 meters in height is also exempt. Another guide can be out buildings that have a lockable door dividing are exempt from planning. Even though you may have been turned down for a conservatory you may well be able to build a veranda onto your home.

Listed Buildings - Can be a very tricky process!
Building onto an existing listed building can be done as all buildings need modernizing at some point in there lives, but at the same time you must keep in line with the building finer detail and style. Also again this can vary from council to council. In most cases veranda can be constructed with the buildings architecture in mind