Firstly, I find it somewhat strange that the carpenters erecting the timber frame and roof trusses would be taken off to presumably expedite second fixing for the end-of-year rush job houses.
It is unlikely they would have the tools, skills or precision required.
It is totally unacceptable that your home should be exposed to the extremes of the weather, especially at this time of year.
A good house builder would properly plan their works, to ensure that as homes are constructed, they are exposed to adverse weather for the minimum amount of time.
A good site manager would also ensure that homes required for builder's year-end are planned and constructed in good time and not rushed. Failing this, he should ensure he has sufficient labour on site to meet the increased programme demands of year-end.
Bearing in mind that one of the few advantages of timber frame is speed, I find it amazing that the timber frame could not be erected and roofed weather tight within 5 days at the most - less if a crane was used.
What you now have is a totally saturated home that will takes many many weeks to fully properly dry out.
You should inform the site manager that on no account should the frame be insulated, the vapour barrier fitted and drylined (plasterboard) until the moisture content of the timber studs is at 20% or lower. This reading should be taken at the sole plate, which is always the last place to dry out.
You should also be ware that the flooring will need to be replaced as even with protection it will have become saturated. Moisture resistant flooring does not mean waterproof!
The composite floor joist may also need to be replaced as their integrity may have been compromised, they are not supposed to be drenched and permanently wet.
Finally, you should also be aware that as saturated timber dries out, it shrinks, twists and warps.
This can and will cause all sorts of issues after you have moved in.
(Bowed walls, excessive cracking, sticking windows and doors, mould, condensation etc.)
If you can, I would cancel altogether.
You don't want to buy a new home on a site as badly organised as this one and Charles Church (aka Persimmon) do not have a great reputation for building quality homes either.
It is a pity you did not find this website earlier, especially the
when to buy and
timber frame homes what you need to knowI doubt very much that this home will even be dry by the end of February, let alone ready for you to move in!