Ok, DH is a tradesman, so from the other side:
We always get customers to pay for parts for big jobs up front because once the item is installed it is yours, regardless of whether or not you have paid for it, and yes, we do have credit accounts with suppliers but they still need to be paid.
Smaller, local suppliers may not offer credit accounts.
He can't always get to your job exactly on time (he may see 3, 4 or even 5 clients a day) because if the client isn't aware of the extent of the work that needs doing he may not allocate enough time for it.
We ask for BACS payments because card readers cost money, and the supplier of those take a percentage of the transaction.
That said, in this instance it's not looking good... personally I would text/send a what's app because there will be proof of having sent it (time/date stamp on when/if it's read too on what's app). Start looking for him on social media, Facebook/Nextdoor would be good places to start, and threats of negative reviews on either of these as well, so many people use either as a platform to find new business that unless he really is a fly-by-night he will care about the effect this could have.
We're lucky to have only lost out by around £5000 worth of invoices not paid in 5 1/2 years of trading, sometimes we've had to resort to threatening a debt collector, but only once actually done so.
I really hope for your sake he is just overloaded and hasn't worked out how to fit the job in, but i think i'd start looking at legal action (small claims) at this stage. I wish you all the best.