hi celine, my information may not be very up to date but before you needed your certificate of non impediment, this depends if you're planning on getting this in Tunisia or in the uk before you go there. If your doing this in Tunisia then you need to be there for over 21 days, your go to the consulate and give notice of marriage and this is posted on the wall for another length of days, cant quite remember how long. If no-one contests this then you apply for your non impediment. They only need to see your passport and you pay the fee and have a little interview. Then when you actually do the contract this is when you'll need a copy of your birth certificate-now this can differ as mine was my original however some need an up to date version and this needs to be translated, my advice would be to get this done locally as its quite expensive through the embassey, you'll also need your medical certificate from the doctor
You only need pay slips and bank statements for visa etc, these aren't needed for marriage
If you visit
http://www.britishembassy.gov.uk/ser...=1022256797639 this will provide you with everything you need
Good luck