It may do, luke, but I doubt it (although it is always difficult to judge from brief descriptions)
If you look at the aggravating and mitigating factors on p202 (but remember these are not exhaustive) you will see that the offence must demonstrate either greater harm or greater culpability to go up to Category 2. As far as the harm goes you have said there were no serious injuries sustained (but see below), the victim was not particularly vulnerable (vulnerability in this context means vulnerable because, say, he was disabled, elderly or something like that) and your attack was not repeated. The only aggravating feature I can see from your description is that fact that you used your belt. This will certainly not go in your favour but it is not the same as using a knife or a cosh (which would involve some degree of premeditation).
I am, however, a little concerned about the injuries. You said the victim spent less than a day in hospital and may possibly have needed stitches. This makes the injuries serious. Further, you said that a charge of GBH was considered. The factor which determines ABH or GBH is the level of injuries sustained rather than any other of the circumstances and the fact that GBH was considered must mean that serious injuries were perhaps present. However, even if the offence is classed as category 2 I still believe that custody is extremely unlikely given your remorse (which your solicitor will explain to the court) and your good record. A suspended prison sentence is also unlikely because for such a sentence to be imposed the offence must pass the custody threshold and I do not believe, even at its most serious, that your does.
These things are never cut and dried and a chat with your solicitor may help you understand the likely outcome. You should bear in mind, however, that regardless of the sentencing outcome you will have a criminal conviction for violence on your record. This conviction will become “spent” after 5 years (if you are fined or sentenced to a community order) which means you do not have to declare it if anybody asks after that time. However some professions and positions are exempt from this and you may always have to declare the offence if you follow a career in an exempt profession. Google "Rehabilitation of Offenders Act 1974" for more details.
I'd be interested to learn the outcome.