I worked for a software house of 10 people. We wore what the hell we wanted unless we were facing clients, then we wore what the hell the client needed to see in order to believe we were professionals. Once the client "knew" us, we wore what the hell we wanted. We grew, we merged with a company of equivalent size to make about 200 people. We kept our "dress code". The merged company exploded in size, technology group represented less than 10% of the 10,000 staff globally a big group of that 10% wore some company branded hooey we stayed with what the hell we wanted. Someone tried to introduce the idea that we should conform to a uniform policy.
I find the requirement for "uniforms" for non customer facing resources to be offensive. I have enough trouble with the idea of "uniforms" for people that do face customers. What I understand is that some customers come at things with a view to what a professional looks like and in order to make the connection you have to conform until you can prove that your suit isnot what makes you worth paying to do your job.
I probably would have walked from my job over this issue because it really sits at the heart of my relationship with my employer. My expertise, commitment and professionalism are measured in what I do and not the clothes I wear. If my boss thinks otherwise then he or she is a tool. If I cannot persuade them or their boss of this issue then the company is not worth working for. Period.
We all have to make compromises and by the time this issue came up for me I was senior enought that I could have pulled weight and just ignored it but I was holding out for all the guys in our group who didn't have that ability. I cannot overstate how much this kind of thing shits me. I don't know about your Helldesk folk but the ones I work with fall into two categories, the good who treat most problems like puzzles and do what has to be done to solve them, for them I would go into bat to get 'em the right to wear what the hell they like. The others, you know the kind I mean, I wouldn't piss on if they were on fire and I have bollocked them and their managers over their work, I would be happy if their uniform was a grey smock and a dunces hat, just so we know what to expect...
If you cannot leave your job then suck it up and wait until you can because this kind of thing is a baaaad deal.