(2-part post):
'Section 18' is defined on the Crown Prosecution Service website:
http://www.cps.gov.uk/legal/section5/chapter_c .html#11
It's only one step below 'attempted murder' in the scale of assault charges but the maximum penalty is the same. (i.e. life imprisonment). The offence is 'indictable only' so, after an initial appearance before the magistrates' court, the case will automatically be referred to the Crown Court.
The whole court process is likely to take many months. The actual time scale varies across the country but it's likely to be at least 6 months before the offender is sentenced. However, the magistrates will review the bail conditions when the case passes through their court and the Crown court will reconsider bail when the case first arrives before them. (There will be several Crown court procedural hearings before a trial - if the offender pleads 'not guilty' - or a sentencing hearing). If either court has any concerns about the safety of the victim, or others, the offender may be remanded into custody.