I don't have a problem with this as long as It's not all upfront at the time of ordering
And the final payment is only payable when the company is arranging an installation date with you
Anyone handing over large deposits in advance of work being done, needs their head examined...that's the real consumer education piece.
Sure, booking deposits are appropriate and yes, perhaps a further element of a deposit for customised items that need to be made in advance, but there's no justification for having to handover 40% - 70% of the price in advance.
You'd be surprised at how many people would "change their mind" if a substantial deposit is not required. Good tradespeople will book the required contractors weeks or months in advance and also order materials. If someone cancels, it can be difficult to suddenly fill that time, but you still have all the costs associated, so 40%-50% deposit is the norm and further payment just before work commences is the norm.
There are many unscrupulous people out there that will do their damnest not to pay if you wait until completion to ask for payment