Advice on how to best format a small claims LBA ?

Theagg

What is best practice for wording and formatting a small claims letter before action, in my case for a job that the trader has so far failed to complete (or even start, I'm even unsure on that, as the agreed work was for an offsite build of items for my garden), despite numerous claims and assurances from him he would deliver them by a certain date, several times. But so far, after nearly two months, has failed to turn up with the items on each of those occassions. (giving a long list of excuses for those)

What to put in the letter and what to leave out etc. At this point I'm inclined to want my deposit back in full plus full reimbursment for the cost of all the materials (paid for by me in full but which he has in his possesion), irrespective of what he may or may not have actually done so far (again, of which I have no idea other than his claims) as his repeated failures to deliver, along with a new excuse each time (forgot it was school holidays, 'personal issues', other things got out of hand, van broken down, being ill etc) has gone beyond reasonable now for me. Am I basically entitled to claim for all that back  ?