So he WAS convicted of battery and got a community service sentence.
If as you say this time he acted in self defence then that is a mitigating circumstance NOT an excuse to commit GBH . You are allowed to use 'reasonable force' to defend yourself, GBH is not 'reasonable force' it is 'over the top'.
We are only trying to find the full facts and give advice, there is no need to get aggressive.
We now also know the reason he has not been bailed, that it is thought he would commit other crimes.
I do not see how we can help. Your BF has a previous conviction for assault and as you say several other warnings and 'statements against him'.
These warnings and 'statements' will still be on his record even though he was not charged at the time. In view of this the CPS have objected to bail.
He can apply again for bail, but the outcome is probably going to be the same.
I think you are going to have to wait for the trial and accept that your BF is going to be spending some time in jail. On the positive side time on remand will be deducted from his sentence.