Very hard without seing it but here is my advice.
*any structure you choose will need foundations anyway.
*you would also need a insulated floor. Either suspended or concrete base.
*you would then decide on upvc or solid structure with tiled roof.
*there is a "in-between" which is building a dwarf wall about hip hight (this wall is to be a cavity wall with insulation and appropriate damp proof layer)
*i usually advise building the wall just a bit higher than proposed kitchen worktops.
* in my experience, a off the shelf upvc conservatory represents a false economy. They are seldom compliant with necessary u-values(insulated) and will almost certainly get very hot in the summer.

So far as cost, for a "permanent structure" with a solid roof. You should be looking at 19 000 to 25 000.

Hope this helps a bit.
Regarded Louis kingwill.

Hi, if budget tight and looking to extend kitchen but like conservatories
Try a garden room, orangry.
One or two side brick/block built for speed, cost and to accommodate your units and appliances. The rest conservatory, plastic/ wood and glass
Thanks

conservatorys are great for the price but are cold in winter and to hot in summer. if your staying in the house for a while have a brick built extension. the other thing to consider is if your cooking alot you will get condensation on the glass in a conseratory.

Hi there
of course you can,modern glazing alows you to have a perfectly habitable room but with the benefit of glass instead of bricks and tiles,dont forget the light,if you extend then you will loose a lot of natrual light,a conservatory will be the best of both worlds you simply need to get it designed correctly so that kitchen units,worksurfaces etc work well.
sean

For a kitchen i would have to say build an extension.
For a conservatory you would still need footings & brickwork anyway so it would not differ a lot in cost.
depending on spec etc id say an exstension would be around the same cost as a good conservatory.

Its not really viable to use a conservatory as a kitchen, a conservatory is going to be really hard to keep warm in the winter, you might find its only usable for 6 months of the year.
An extension can be used all year round, and would probably add more value to the house.

If you were to do this to building regs then it wont be your run of the mill conservatory,You will have an extension (minus a bit of brickwork) with a glass roof.Cant see you saving any money going down this route but if done properly, they can look great.If you try and cobble something together on the cheap,it will be a big mistake.Presumably there is no way to increase the existing kitchen size by making internal alterations then?