I am about a month behind the schedule in my mind. My signing-up with a timber-frame company was delayed as my favoured company moved their factory over Christmas. In the end I seriously considered no less than seven frame companies, met with five, and visited the factories of four. I have now chosen the company and will be signing on the dotted line soon. It is a local Cambridgeshire firm and represented for me the best balance between cost, their approach, and the personalities involved.
Observations from the last month:
Old Buildhub searches work well. I have text shortcut the throws the following in to a google search: "site:buildhub.org.uk". That enables effortless searching of the Buildhub archive for any string. For example, when thinking about which SE to use to design my slab, I threw "site:buildhub.org.uk Tanner" into Google a re-read the posts by @Alexphd1, @Triassic, @RichC and others, some of which were years old, arranged a call with Hilliard himself in Ireland, and all my problems went away. Same applied for bolstering my list of raft installers and a host of other subjects besides.
I looked again at the make-up of my roof and foundations. My dwelling has a ridge height limit in its deeds and I want high, 3m, ceilings. I went around the houses on both subjects (thanks to you all for your contributions to my threads on the subjects). On the roof I ended up somewhere new, and flipped form a cold to a warm room, and saved about 200mm. On the floor, I ended up back where I started, with an insulated concrete raft attached to screw piles but, with the help of Hilliard Tanner, it will be a thinner 100mm raft, with strengthening ribs, and a 200mm ring beam. Because the raft will be tied-in to the screw piles the insulation beneath will not be load bearing. This means that PIR will work just as well as EPS as insulation. PIR is thinner for a given U-value so once again I will be saving about 200mm of thickness.
Resolving the issues the ridge and front-door-threshold heights then enabled me dive deeply in to the levels. I have a small but complex plot and deciding levels took quite some head-scratching, especially as my site is supposedly "no-dig" because of previous tree roots. Levels are now done I think.
With all the fundamental decisions about the build now resolved, the cavalcade of actions leading up to the start on site can now begin in earnest: frame design, engineering inputs, construction drawings; planning-conditions discharge (and maybe non-material amendment); tenders for groundworkers, screw-pile suppliers and installers, raft makers, rooflights, windows; site insurance, building control, warranty.
Oh, and I have re-designed the façade once again.
All systems go! Spirits are high.