Once a person is convicted of an assault charge the judge has to decide whether there was greater or lesser 'harm' and also whether there was greater or lesser 'culpability'. Based upon how he/she assesses those factors it will then be determined as to whether the offence is classed as 'Category 1 (with both factors 'high'), 'Category 2 (with one of the factors 'high' and the other 'low') or 'Category 3 (with both factors 'low').
Based upon what you've written it's likely that 'culpability' would be seen as 'high'. It's possible though that, despite the extent of your injuries, 'harm' might be seen as 'low' within the range of GBH offences which come before the courts. (i.e. the 'high' category might be seen as only applying to cases where, for example, the victim suffers a permanent physical disability).
So it's either a 'Category 2' offence (or, if both 'harm' and 'culpability' are seen as 'high') a 'Category 1' offence.
The 'starting point' sentence a 'Category 2' offence (from which a judge must work up or down, depending upon the circumstances) is one of 6 years' imprisonment. The 'starting point' for a 'Category 1' offence is 12 years imprisonment. The actual time that an offender will be 'banged up' is normally half of the nominal sentence.
See pages 3 to 6 here:
http://www.sentencingcouncil.org.uk/wp-content/uploads/Assault_definitive_guideline_-_Crown_Court.pdf
(That's the actual document which the judge must refer to. He/she can't go outside of the guidelines given there other than in really exceptional circumstances).
All of the above assumes, of course, that your ex is found guilty. As NJ indicates, you will need to be strong to ensure that he is.