get your backpack as soon as you can simon,i bought mine in stages about 4 months ago,backpack and pole one week,r/o+di the next,i fill 6 barrels the night before and bring the di with me for top ups. it makes windowcleaning far easier/quicker but it does take time to get the hang of so id advise sooner rather than later,i too was confused as to how the whole water fed pole thing worked and found the best way to understand is to get a supplier to show you the lot,once shown it looks simple,consider second hand to keep costs down-i got my 300gpd r/o for £100 and ive heard you can get backpacks off ebay us for around £120,make sure you get a long enough pole and get a tds meter,dont worry about learning trad-its easy