Best of luck for the future Nick. Been there myself when my biggest customer went bang. carried on for 5 more years but I was always finding it hard to clear the bills. In the end I called it a day, I have been far better off since then.
Even now I still fancy giving it another go, Luckily I have managed to stop myself.I do think haulage gets in your sole, it must be like giving up drugs, its always in the back of your mind and before you know what’s happening you set up another company for more heartache and a lot of stress 
I do hope things sort their self out and you can bounce back.