I am completely clueless when it comes to matters of building! We would like either a rear extension possibly 2 storey. Or, if it's possible, a two storey side extension but have no idea what is a better option or achievable. Where do we start? Find a local builder to have a look or do you have to get plans made first? Any tips would be appreciated!
Probably deciding how much money you can spend on it will dictate whether you can have a single or double storey extension. Second, look around at houses in your street and similar local streets - has anyone done similar work recently? That will inform you what the planning authorities would be willing to accept - single storey extensions may fall within permitted development and not require consent.
If you do see a house that has an extension similar to what you would like, go to the local authority website and see if you can download plans. You can then show them to a builder to get an idea of how much money it would cost (although it will always cost more than they say). If you can afford that ballpark figure, you can go about hiring an architect or surveyor to draw up plans to your specifications, try to get consent if necessary then go about choosing a builder.
We are in the midst of an extension. When we started thinking about it we were told by builders to allow approx £1200 - £1400 per square meter as a rough guide for extensions costs. Ours was more tricky because the extension part is only 9m2 but we are removing lots of walls to make 4 rooms into 1 big open plan space so it's costing approx £40k in total.
Find a good architect who will discuss all your options with you. Ours redrew our plans about 100 times so that we could visualize different options before we applied for planning permission.