Hi Furiousfairy,
I'm so sorry to hear about what is happening to you and your boyfriend. My boyfriend is currently going through a similar process. He has been charged with assult on a bouncer who actually came out to hit him! My boyfriend is also pleading self defence and it is going to crown court (he asked for it to go there for a fair trial).
I did have a strong belief in the justice system but slowly as I am finding out details of how the law works my belief is going.
All I can suggest is go through the statements very carefully, luckly you have CCTV which should help your boyfriends side of the story (the police failed to get it for us so we don't have that as our defence evidence). Have you seen the footage? If not, ask your solicitor if you can. Despite the issue of race what happened was wrong and hopefully the jury will be able to see that. The taxi driver should of stayed in the cab, whatever was said...why did he come out of the cab??? that's not a reaction of someone who wants to just have a chat or be nice especially if he has been arguing with your b/friend seconds earlier!
have a look at the cps website, it gives some information on self defence.
http://cps.gov.uk/legal/section13/chapter_t.ht ml
I know what it is like being a worried girlfriend and stressing out with what is going to happen.
Good luck with it all. Let us know how it goes.