It's very important that the ground is as flat and level as possible. Any slope will put extra pressure on the down sided walls.
Invest in a good sand filter pump, economically it will be better than buying a cheap one and having to change the sand more often.
For heating we bought an air heater. Cost was near £700 but it paid for itself by the savings in electricity. Using the supplied 2.8Kw heater we couldn't get the temp over 21-22C
Using the air heater we could get it to 34+ overnight. The problem with our pool was it fed the heated water in at top level which created a lower cold level so we used to stir it with a large paddle before getting in. This tended to lower the temp to around 30-32C so was still comfortable.
Our pool was quite large, 12' x 16' x 4' deep so took a lot of water, (thankfully we were not on a meter LOL). Here are some pics taken during construction. I did have a few of the pool full and an adult in the water, which would have given some perspective of the size, but can't find them. Maybe if I tell you it took me 5 full crawl strokes to go from one end to the other you can get an idea. The plastic box housed the filter
& pump and the air heater was situated to the left of it
One final warning. DO NOT kick off from the side walls!
The bricks around the edge are roughly placed and purely decorative and hide the pipe works to the left.
