Thank you for your enquiry.
The advice we provide on our site is general and not specifically linked to individual personal preference. Even though we would suggest a medium spring tension, we would always take personal preference into account when advising upon the right mattress.
Given your budget, the mattress which would best suit is the Artisan 1500 which has 50/50 natural fillings and man made fibres but has a firmer top layer than the Artisan Naturals which you found a bit too soft. This mattress can be made with a firm spring tension to suit your specific requirement. The Artisan Naturals which you have slept on has 85% natural upholstery, which is the most you will be able to get in that range for your budget.
Our Artisan Bespoke is a mattress that has 100% natural fillings but has a firmer feel in the top comfort layers which I feel would be better for you both but it is more costly due to the fillings in that mattress.
We trust that this helps, but if you require any further advice or guidance, please call our office on 0161 437 4419 and speak with one of our advisors.
Kind regards Julie