OK, we (bf and I) have spelt our dream out:

a house, sustainably built, if possible round. Thinking of cob or cob and stone. with the south-west face of the house mostly glass.

Initially, I would think 40 square metres on the ground. two storeys. ground floor would be the living/cooking area with one loo.
first floor would see two rooms and a shower+loo.

Ideally, there would be a small attached building with the animals on the ground floor and maybe some kind of room above.

rain water harvesting, solar/wind power. extra insulation. and outside blinds like we have on the continent to minimise the loss of heat through the windows in winter.

Any thoughts, you brave people?

Sound idyllic! When ya gonna build it?

I would be careful with a wall mostly of glass....overheating in the summer, and huge loss of heat in the winter.
You could have the rest of the house insulated from the room with the glass, but then ya lose usable space.

Having a bolt on (but done in a way so it looks part of the design) conservatory on the south west side really works if done well. With openings in the top to vent in the summer, and an insulated wall between it and the house allows it to act as a large heat capturing device in the winter where the hot air can be taken into the house through small windows in the wall.

You can see Jonnie's house with the two storey conservatory which in even a little sun in mid winter can be quite warm. You can then use single glazing in the conservatory, whereas if it was part of your main wall you would need to use double glazing to ensure you didn't fail on the SAP calcs for building regs. You can see in the photo the openings at the top to let the hot air out in the summer.

Another photo of jonnie's conservatory from the front.

woaw! that looks good!

Actually... small issues:
We don't have the money,
We don't have the skills,
We don't have the land.

it's going to be great!

(and I am not even sure if I want bf in that house!)

Land, yea difficult
Money, even harder...but you can build to what money you have or can get hold off...check the £4000 house.
Skills!, don't worry about those, there are plenty of peops about who are normally more than willing to give advice, especially if they got products to sell. You will gain lots of skills though!

Whats wrong with bf in the house?

Am I wrong in thinking that (at least part-)self- building an eco-house could cost no more than a normal house in town?

At least, I've got the dream and the will... now I'll start looking for skills (but I am good at project-managing).

bf is lovely...not so green, though.