Your products vs. Vi Spring

Hello there, I am currently using a Hypnos Regent Supreme (medium tension) and its giving my lower back aches and shoulder aches even with a two cm latex topper. I am 178cm, 65kg. Previously I used the Hypnos Orthos Cashmere and that was worse. I suspect there are a few reasons for my aches - the springs are too hard and the filling on top is not plush (and at the same time not resilient enough). Previously I tried 5-zoned mattresses that provided firmer hip support and softer support on the shoulders. Strangely, my hips were not painful even with a firm hip support but I wake up very morning feeling an ache in my upper back. I think the soft support on the upper back coupled with the firmer support around the hips caused an imbalance in the spinal alignment when I lay on my back.
I happened to try a Vi Spring Shetland (they only have medium tension) in a showroom in Singapore (where I live), and it felt good as I first lay on it. But I was worried if the pure wool upholstery would provide enough resilience so that my upper back does not cave in too much when I lie on my back, but would give in enough as I sleep on the side. I was intending to buy a Vi Spring Shetland online and get them to lock in the sale price for me while I decide the spring tensions when I visit a showroom in London in September, but found your website. And prices are almost halve, so I though I would write in and see whether I can find any alternatives.
Let me know if its easier to discuss on the phone. I can call you while I am in the office.