I think between Anker, Aukey and Spigen each company offers something to suit everyone’s budget.
Aukey has a 20000 mAh basic yet functional battery bank for just £20.
Spigen has a midrange 20100 mAh battery bank for around £33.
And Anker has the premium and fantastic looking PowerCore Speed 20000 with PD for £50.
Ankers build quality and customer service for me is worth the extra money every time if you have it to spare.