I'm amazed that it's being tried in a Magistrates court. While GBH is technically an 'either way' offence (meaning that it can be heard either by magistrates or before the Crown Court) it is nearly always passed up to the Crown Court, simply because the magistrates recognise that, if the defendant is convicted, their sentencing powers will be too low.
The maximum sentence before magistrates is 6 months imprisonment (plus a fine of up to £5000) but the case could still be referred to the Crown Court for sentencing, where the maximum sentence is technically 5 years (but actually 4 years within the standard sentencing guidelines).
See page 198 here for the magistrates' guidelines on sentencing GBH:
http://sentencingcoun...ate_1__2__3_4_web.pdf
See page 8 here for the Crown Court guidelines:
http://sentencingcoun...ine_-_Crown_Court.pdf
If sentencing was before the Crown Court I'd expect the other charges to be largely irrelevant because any custodial sentences would be likely to run concurrently. However the Magistrates might impose concurrent sentences.
If the GBH offence really is at the lowest end of the scale (but with the aggravating factors of a previous conviction for violence, plus the additional charges) I'd guess at a sentence of 4 to 6 months imprisonment if the case remain before the Magistrates, or around a year if not.
Chris