Barbara pretty spot on. Sand on base is best for temporary situation and you can leave it when the pool gets put away for winter. Another way to level is setup up a string line in a square ie. 4 stakes to hold it up and level the string line. Use the string line as a visual guide and you can also measure down from it as you go. As you dig the higher ground, you effectively move it the lower end. Saves having to get rid of dirt and you can restore it to its former natural slope when you returf. Compact the fresh pile at the lower end and use the rubble to help hold it together. Your other problem of turf not growing in that area has little to do with the rubble in my opinion. Does it get plenty of winter sun? Do you feed it/water it regularly? I grew over 20 sq. metres of turf on a cement slab in my yard with only 100mm (10cm) of dirt which also had concrete rubble mixed in. It had no direct sun in winter but still stayed green throughout, beautifully in summer. Good luck.

Thanks everyone for your comments so far. Bowmandrum , I definitely agree you need to tick as many boxes as possible for potential buyers. In answer to a few of your questions, we are in Sunny Brisbane, so the weather is not really an issue. However, our dilemma between a pool and spa is the very difficult access, the size of machinery dictates what we can actually accomplish. Hence, from our point of view it very much is a case of asking the question, if we can only manage a spa - will people appreciate it/want it or is it not worth it. Based on feedback with the poll it looks the spa will be worth the investment.

What a great pool for starters. I do see your dilemma though. For the fence: I would give it a paint, choose a colour that ties your house in. Add laser cut screens or put in a vertical wall garden as you don't have a lot of room to have a row of pots. In saying that a few large pots around are great to add some interest and colour. Strelitzia's are great plants to use. Tough, can handle sun, lovely bright orange flowers. Certain sun loving bromeliads, great colours. Clumping palms are always a winner. Just watch yuccas, as previously suggested, as they are often spikey, with kids running around I would stick with softer foliage. Somewhere to sit is always important but again you don't seem to have a lot of space and you don't want to overcrowd the area. Perhaps a long bench seat along the far fence, include outdoor cushions and built in storage under seat for pool toys. A large umbrella in the corner for some shade. All of these can add colour while being practical. However I do like the idea of extending the back pool fence out to create more space, Bali hut here we come! This may not be an option.... Good luck, I'm sure with a bit of planning you can turn this into a beautiful space for everyone to enjoy.

watchedpoppy, here's something about heat pumps designed for cold temperatures. Note, these are reverse cycled air conditioners (air-to-air), not pool heat pumps (air-to-water). I don't know how heat pumps stack up. It's an American site, so FYI -13F equals -25C. http://www.mitsubishicomfort.com/benefits/hyper-heating On a side note, temperature is just the product of the motion of atoms & molecules (kinetic energy). These are in motion all the way down to zero Kelvin (-273C). So although it may feel cold outside, there's still energy available in the site, although heat pumps do become much less efficient when it's cold (the difference in input & output temperatures is important). One thing that has made heat pumps very inefficient in the past is that the condensing coil would ice up at around zero C. This would have to be thawed out with a plain old electric element (COP of 1). Greatly reducing the overall COP in temperatures around our below zero C. But the modern heat pumps, which use the CO2 compressors Luxury Home Heating has talked about don't have an electric element to thaw them out, greatly increasing their efficiency. As for the noise issues. Some modern heat pumps (but not all) are very quiet. So just pay close attention to the decibels they produce, listed on their spec sheets. FYI, here's a good read. Though it doesn't mention solar PV, which would be advantageous for a heat pump. https://www.pooledenergy.com/blog/choosing-a-pool-heater-what-are-the-relative-performances-of-solar-gas-electric-pool-heaters/