The certificate of no impediment was translated at the Embassy, think it was around 170 dinar. I got my birth certificate translated into French or Arabic at a local translators in Sousse, think it cost about 10 dinar. We also got my husband's birth certificate and bulletin 3 translated into English at the same place also cheaply, it wasn't a requirement for the visa, but thought it would be useful when he arrived here and it might add weight to the application. I enclosed loads of weekly pay slips and one printed on-line bank statement which was recent at the time, and one 5/6 month building society statement, both statement where looking good, but previous ones weren't and I wasn't sure what they'd think if they saw me being overdrawn
and a small overdraft, so the payslips help me out a lot. To be on the absolute safe side bring 6 months worth of statements. I think I was lucky! Good luck with everything.