This is a bit of a sweeping statement and I apologize in advance to the many tradespeople who act with integrity and demonstrate a good work ethic, but....
History has shown me that there is just a different sense of commitment and priority in building/diy/decorating than I am used to in my 'work world'. If I say I am going to be at a meeting/on a call/at a place at 10am - I just am. I have encountered enough builders/kitchen fitters/plumbers in my life to know that "I'll be there tomorrow at 10" doesn't mean that they will. It means that at the time they said it, they thought they could probably squeeze it, but should another job run over/a more lucrative job pop up/anything else crop up - I will just be bumped until my job becomes their priority.
It is often not even a reflection of skill or someone being 'nice' - it's just a shit work ethic, an inability to time manage or organise and poor communication skills.
No excuses, but just to say, that he might not have started out planning to do a runner in a spiteful/crook way, but may have now lost control and overspent your money elsewhere - just through general shitness.
I would be inclined (only to save my investment) to send a message saying "Look, you're clearly snowed under or up against it, but I do need a definite date so that I can plan my day and stop thinking you are trying to rip me off. I was really happy with your work and don't want this to end up getting ugly. If you can't now do the job, I understand and we can arrange for you to drop the materials here. Please can you just update me?"
It's more than he deserves, but it's probably your best chance to getting the work done and realising your money.