Just a 4 SQ metre ground floor extension with a pitched roof and French doors. It won't interfere with anyone's light or overlook anything. Just a box really so nothing complicated. Attached to side of house with a smallish footprint.
Do we need an architect?
Apply to the council for planning permission?
What work can we do ourselves to cut costs?
Best place to source bricks etc? (We want to source everything to cut costs)
Have a look at your local authority website - Planning Department and also Building Regulations.
I have just posted an answer to a similar question so read that but you want to know about DIY and saving money so this is what you need to know: Usually if the extension is 3 m or less from rear walls you do not need PP (do check about your own situation). Permitted development means you just need building regulations approval. You will not need architects drawings you can do your own sketches - they are good enough.
The things to do first are: print off the Local Authority Application form for Building Control Permission and consider how you will complete it. At a later date Building Control will ask you about construction details to do with insulation and materials used but you do not need to worry about that straight away. Even though you want to save money I would employ a professional ground worker to do the foundation for you. A real professional will know how to meet the requirements of current building regulations. Your ground works need to be inspected by the BC officer to make sure footings are deep enough, they are far away from drains, insulation is adequate - this is all so important you do not want to get this wrong.
I would not just employ any team of builders who say they can dig a whole and lay your foundations, go for real full time ground workers - more expensive but it will be so costly if it all goes wrong cos you employed cowboys with a couple of spades.
Bricks, etc - talk to your local small/ independent merchant - they might give you discount if you ask.
By nice to your Building Control officer, talk to them and think of them as your friend and they will tell you what you need to do to make sure you comply with the rules as you go along.
Check that do you have full permitted development rights. If the house has had extensions in the past, porch/garage/add ons or you are in a conservation area or an area with reduced rights (some new estates)