CT - I am sure there is an online application form, however as you are in the UK you need to keep trying the embassy. I can't tell you exactly how long it takes for you visa but you need to apply well in advance of your travel here.
Shelley - I did forget to just warn you about advice you receive. Alethia is a first rate immigration lawyer and knows intimately the laws in regard to this subject. I am an expert in Tunisia having lived here for many years. I understand this culture, society, the language and the naughty little boys who live here with a desire to live elsewhere. Please take care - Alethia and I are here to assist and ensure that you get the correct advice.