Many suppliers will put dry clean only on their curtains (including the custom made ones) to protect themselves from people mishandling the fabrics and if there's a block out backing on the curtain then this might not be washable. Linen will shrink if you put it into a hot washer or dryer but as Julia has indicated linen is a beautiful fabric to use if you do the right thing by it - if your wanting linen for the block out use a fabric backing rather than a linen that has a coating and make sure that the block out fabric can be separated from your linen fabric (curtain makers will hate it as it's a nightmare double handling, but if you're going to spend a lot of money on linen and for them to be made, it's not unreasonable to request this.

Hi Kate, do you have any floor plans or pictures which will help us visualise the areas?

Can you extend the porch to 2.9m wide to fit a table. It does not need to be for the full 14m perhaps just 4m and not near a door. Also consider metal supports and tensioned wire which can look lovely and also is low maintenance. I'll try and find some photos of what I mean if you are interested in this concept.

First up talk to your local Council around their requirements. You may find there are hoops to jump through. Have you had a price from a plumber for the sewer connection? That will be the most expensive part. And for materials - there are generations of outdoor loos made out of corrugated iron - so Colorbond would be a solid choice.