Thanks :) Yeah decided to go with tile. So sand cement is ok over existing tiles if I prep them first? Only problem is, the new pad can only be about 30mm at it's thickest (leaving up to 15mm for tiles) otherwise it'll end up being higher than the hallway floor. So I either need to make the fall shallower or not bother with the waste and make it all level. If I made it level, could I use levelling compound at that thickness or would deck mud/sand cement be the best option? Also, should I be putting in mesh for strength? (I know I should (and will) ask the local hardware what they suggest, but it's great to have suggestions from the Houzz community also)

Hi, Thanks for the response. :) I am following CCC Residential Suburban and Residential Suburban Density Transition Zone. It seems you can build 1m from boundary without having a window facing the boundary. I thought it seemed close, but if it gives me more space on the sunny side of the property then I'm happy. I wasn't sure how worthwhile it was me building interior/external walls into my design. I think a real draftsman would only use my dimensions as a guide and bin my project designs. I've only used the boundary line to design the entire thing, then used some Objects to give a visual guideline.

You DO have a steep slope to deal with! The tree roots will help stabilize the soil and make a mudslide less likely. If you cannot mow the lawn safely, terrace the area (think Machu Pichu) into garden beds for flowers or vegetables. Do you want your children to play on a grassy area or on a man-made surface? Be sure that the play area has shade during the hottest part of the day. Best wishes.

I think you are wasting money . I'd leave the columns , do a couple of bi-fold aluminium doors , do a nice leather corner suite , and artwork , a Tv , make it more livable . I'd do a glass balustrade on the small stairs , 3 or 4 creeper type potplants and a couple of 'objects d'art' along the solid balustrade . Do you have another dining room ? If yes , make part of this an office/study ; if no , then a nice table and chairs . Right now , it looks unloved -- make it easier to fall in love with it , and you will !