Hi all. I'm going to attempt to install a drainage run myself for the first time for a new extension/annex in the garden. I'm a little confused and wondering if I can get some advice. Why do some companies offer a choice of "budget" or premium? Is tghere anything I should be worried about as there is a big difference in cost? Here's the link to make it easier: https://www.easymerchant.co.uk/underground-drainage/inspection-chambers/ help greatly appreciated!