Keep in mind that I am building this dwelling primarily for my enjoyment of the process and journey, and as a learning experience. I am therefore optimising for my own involvement, which is close to full-time, not for the usual triad of price, time and quality (although from that triad, I choose price and quality over time).
I'm sightly reluctant to name names on this public forum as it may be unfair to those I did not choose. I would be happy to send you a PM with the names.
In general terms, my long list was about eight frame-companies. I visited the factories of two and spoke at length with about four. Unusually, I was quite opinionated about the frame build-up that I wanted and so was looking for that flexibility. In the end I chose the company that offered that flexibility and which also happened to be a local company, not halfway across the country.
I learnt, with the benefit of hindsight, that it is perfectly possible to take a different approach. Having now also been introduced to an excellent and personable frame designer, next time I might start with them and ask them to recommend a frame-manufacturer in the local area of my next build, wherever in the country that may be (frame manufacturers are the clients of frame designers).
I learnt that it is perfectly possible to work with the various parts of the supply chain oneself, such as pile designer, foundation designer, frame designer, roof designer and make it all work, and not resort to using a one-stop shop, with the inevitable constraints that provides.
I didn't choose a standard package but invented my own. Its a bungalow:
Foundations: a complicated and completely bespoke solution. Screw piles, 240mm heave protection, 230mm PIR insulation (not the more usual EPS), reinforced concrete raft (with UFH pipes and lots of other pipes and ducts embedded within it, including the potable-water distribution pipes). Three embedded recesses in the concrete (two shower-formers and a mat-well for the front door).
Frame: 240mm I-beams full-filled with woodfibre insulation (either Wamrcel or woodfibre batts, I am still choosing). No internal walls: I will do those myself in metal framing. A single steel beam.
Flat green roof: warm roof, by Bauder for the transferrable warranty and no worries about leaks. Bauder is also installing the extensive green-roof atop.
Nine roof windows.
Passive-house-style front door (the only external door).
I chose this as I had read a lot about frames and wanted my chosen balance between thickness (which steals floor space), U-value, decrement delay, acoustic insulation, and greenery (saving the planet). I will be interested to see how this frame preforms.
Yes, two of the big national firms did. But that was actually of no interest to me as I want to do the airtightness process myself anyhow to see what sort of results I could achieve.
(By the way, I simply could not have done this without BuildHub!)
Hope that's helpful. Of course, it is only one personal view and, as you may have gathered, I am somewhat unusual in my motivations for building. Others, and there are many here who have much greater experience than I, may be able to provide insights that align more closely to your own personal circumstances.