Hi urvgotti,
It sounds like you’ve done some good in person testing of mattresses, which is great! I’m not a mattress expert and don’t have any personal experience about Berkeley Ergonomics mattresses, but hopefully I can give you a few things to think about and provide some links that might be helpful in your research.
Here are a few other forum threads that have discussed Berkeley Ergonomics mattresses (you can find more using this forum’s Search function):
https://forum.mattressunderground.com/t/vispring-leesa-legend-or-berkeley-ergonomics-oslo
https://forum.mattressunderground.com/t/new-to-group-new-to-mattress-buying
https://forum.mattressunderground.com/t/split-king-ca-king-latex-mattress-adjustable-frame
https://forum.mattressunderground.com/t/deciding-between-berkeley-ergonomics-models-oslo-and-malmo
Many of your questions are about whether the price of the BE London is worth it. That’s a difficult question to answer, because so much of that is dependent on your personal values. Can you buy a quality mattress for less? Absolutely, especially considering that natural materials aren’t part of your personal value equation. Natural (especially organic) materials are more expensive, and you will generally pay a premium for mattresses that contain them. I understand your hesitation to buy a mattress that is charging a premium for a characteristic that you don’t care much about - but it also sounds like you find this mattress more comfortable than any other you’ve tried so far.
You mention comfort being your primary consideration. A question you are probably asking yourself is - will you be able to find a quality, less expensive mattresses that is as comfortable as the London? Difficult to say, but it seems worthwhile to try as many memory foam / hybrid coil mattresses as you can, to see if a high-quality but less expensive alternative exists. If you are unable to find one that you find as comfortable as the London, then you have your answer on “is it worth it”, since your primary consideration is comfort and it wins in that category.
Related to quality/value - you may want to familiarize yourself with durability guidelines related to memory foam:
It’s nice to know that the London has a zippered cover, so if the memory foam is the weak link, you can replace just that layer.
On the foundation - make sure whatever foundation you purchase meets the requirements set forth by the mattress company (most mattress warranties will depend this). For instance, you’ll often see requirements regarding how close together the slats should be. The type of foundation required will vary depending on the mattress construction category and to some extent, the brand/retailer. I’d recommend asking the mattress retailer about this before deciding what foundation to purchase. You may find the following post helpful in terms of researching foundations sold by Trusted Members of this site:
https://forum.mattressunderground.com/t/what-kind-of-foundation-to-choose
All the best, and keep us posted on how you’re getting along!
Emily