What's the best mattress for us?

Hello,
My husband and I are looking for a mattress and would like your recommendations of what is best to ensure a good night sleep. Below are our details.
Mattress:
- 200cm x 180cm mattress non-zip
- For easier handling we are open to a zip mattress however have some concerns: can one feel the gap even with a topper on and we tend to both sleep towards the center effectively lying on the edge of the mattresses so I am concerned that overtime this could damage the edge of the mattresses.
Mattress Topper: With the size of the mattress we want there is only one topper that John Ryan offers that will fit a 200cm x 180cm mattress. It’s my understanding that toppers are important to use for added comfort and should be selected to compliment the particular mattress one chooses so it’s surprising that John Ryan has few choices to select from. Why is this the case?
Mattress Recommendations:
Weight & Height:
Andrew - 185 lbs & 6 feet tall
Eleanor - 98 lbs & 5 ft tall
Base:
It’s our understanding that not only is it important to purchase the correct mattress but to also purchase the correct base as it plays a role in the comfort of your entire sleep experience. Which option would be best? Bonnel Coil or Pocket Sprung? Also, will having drawers vs. no drawers effect the quality of the base?
Back Issues:
I have mild sciatica and have upper neck pain on my right side. My husband has no back issues.
We did the usual quick few minute test lying on our backs and sides testing some Vi Spring models. For what one can tell from a short test, we both liked the Regal Superb medium, we also liked the Heaven mattress topper. I found the Devonshire too soft as did my much heavier husband. What mattress, base, topper and support stiffnesses would you recommend and why?
We most likely will not be able to take advantage of your 30-day guarantee as the items will be shipped to Spain so it’s important that we are able to purchase the right bed for my husband and myself.
Thank you for your help.
Regards,
Eleanor