Geoff, I am making a square 4 pack, 70 x 42 approx, soldering copper strips 6 x 1.5 mm with an 100watt iron, don’t want battery getting hot, and a friend is making some 3d printed end caps. I purchased 8 batteries at £61, from Cell Supply, they have two sites one for commercial and one for private buyers, you are correct it’s £41 about for four from the private site. Minimum order of £50 from the commercial site. Also adding a balance lead so charging will be same as for a li Po, as per the videos.