Prosecutors can ask a Judge to admit evidence of previous convictions where the prosecution alleges that they indicate a 'propensity' to commit the type of offence with which the defendant is charged. (Such applications are normally only made/granted in relation to sexual offences although they can be used in other types of case). However, even if you'd actually been convicted of GBH with intent several years ago, it would be extremely unlikely that a Judge would grant an application to introduce 'propensity' evidence. Without any such conviction there is no chance whatsoever of the earlier matter being referred to in court.
A GBH charge can only be sustained if the injuries to the victim are 'really serious'. With regard to that, the CPS's own guidelines state:
"Grievous bodily harm means really serious bodily harm. It is for the jury to decide whether the harm is really serious. However, examples of what would usually amount to really serious harm include:
injury resulting in permanent disability, loss of sensory function or visible disfigurement;
broken or displaced limbs or bones, including fractured skull, compound fractures, broken cheek bone, jaw, ribs, etc;
injuries which cause substantial loss of blood, usually necessitating a transfusion or result in lengthy treatment or incapacity;
serious psychiatric injury. As with assault occasioning actual bodily harm, appropriate expert evidence is essential to prove the injury".
The addition of 'with intent' to a GBH charge does NOT (as you seem to be assuming) imply 'intent to kill'. It simply means that there was intent to cause the grievous bodily harm. The CPS guidelines state:
"Factors that may indicate the specific intent include:
a repeated or planned attack;
deliberate selection of a weapon or adaptation of an article to cause injury, such as breaking a glass before an attack;
making prior threats;
using an offensive weapon against, or kicking the victim's head."