Using cellphone batteries to build a big power bank
One of these days I'll write a definitive Lithium charging article. Until then, I refer people to http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

You can get ICs that do one cell at a time, which are about £0.50 each. Two cells in series is more complicated due to the need to have a balancing connection in the middle.

Your best option is probably to find a charger designed for R/C car packs having cells in series, which will come with a balancing connection in the middle. Then build your 4+4 pack. Note that each cell should be at the same voltage before parallelling; connect them together first via 10R power resistors for a while to give them a chance to equalise.