Racially aggravated common assault can be tried in the Crown Court and the maximum sentence is 2 years imprisonment.
Simple common assault (or battery) carries maximum sentence of 6 months imprisonment.
The court can, of course, impose lesser sentences, if convicted, such as a suspended prison sentence or a community based penalty such as unpaid work.
The Crime and Disorder Act 1998 says at section 28: "...at the time of committing the offence, or immediately before or after doing so, the offender demonstrates towards the victim of the offence hostility based on the victim’s membership (or presumed membership of a racial or religious group..."
Telling someone to "go back to your country" is likely to fall into the category of 'racial group' as defined above.
If you acted in self defence and deny the level of violence alleged you should think about pleading not guilty and having a trial in the Crown Court in front of a Judge and jury. You might stand a better chance in front of 12 people in the Crown Court than 3 Magistrates.
Hope this helps. Happy to discuss further if needed.