Thanks forum member.
I agree with you on number four actually - I hadn't thought of search engine problems.
And having never used SSI before I wasn't entirely sure about it - if it's complicated I will follow your advice and stay clear.
I should have made it clear - I'm not going to be the only person updating it. I am going to create it and perform large maintenance tasks but small updates are going to be done by other people who aren't as computer literate as me. Is there an alternative to a CMS for updating the pages easily by someone who doesn't have a great HTML knowledge? (These updates will probably involve changing small bits of text and maybe adding images. There won't be many 'big' things because I will be dealing with them in Dreamweaver.)
£1m? Of course! Make it £2m! :D