Hi there yes we had si,liar problem OH plasterer self employed. We did stat decs and also got 9 references in total of previous jobs (two of them were off regular builders he does work for and in letterhead) we also got a letter from our accountant and sent his tax records and ni contributions for last 12 years! I'd order these now as they can take upto 12 weeks to get you just need to make a subject access request to tax office I"ll try and find the link and send it you on. Basically get as much info as you can as they are quite strict! I sent tax certs, yellow images ads, references even receipts for building materials!