This is all excellent advice. Your GP and your local ergonomic advisor might be well-meaning, but they tend to target the site of the pain - which often arises as referred pain due to nerve pressure elsewhere. (There's a lot of unnecessary tendonitis surgery being performed as people mis-diagnose carpal tunnel syndrome, etc.)
Go see a physiotherapist; ideally one who you've had recommendations of from a fellow sufferer. You sit for eight hours straight in a terrible position: your back and neck cramping up, your traps tightening defensively, and so on, and the place you're gonna feel this is not the place where the damage is occurring. A few sessions with a decent physio (and an easy exercise regime which you FOLLOW - use your workrave breaks to do these stretches) can turn this around. It's your livelihood you're talking about.
Anecdotally: about three years ago I had terrible RSI symptoms - so much so that I actually thought my career was over. I did a whole bunch of intensive physiotherapy (after my GP helpfully and very rapidly started talking about surgery - well-meaning, but not informed) and it pretty much saved my quality of life, my ability to earn, and my mental health.
Don't look to "cope" with this. It's typically fixable. Talk to an expert. There's a simple cost-benefit trade-off.