Re: £700 for a decent chair
The posture is part of it but if you have a really wonky chair, your body will automatically compensate for the wonkyness and adopt a weird (and possibly painful) posture. I had one yesterday that looked fine but was subtly out of kilter and my back started aching after 15 minutes. Swapping for another one (same model, less wonky) immediately relieved the pain. So a good chair is one that enables you to adopt a good posture and can also survive an office environment many years without breaking. Such chairs are not cheap but well worth the investment.