@duncanc Sorry to hear about your computer; hope the new one does what you hope!
Regarding the themes, the change seems to be OK on both Dressprow and Trevelin. The input field is styled differently (sspecifically a different height and rounding to the others on Dressprow), but it’s not a problem that need block the patch in my view.
Regarding field length, this is more of an issue, as currently the field width is taken from the length of the default value. If that happens to be very short (e.g. default country is UK) then the menu becomes unwieldy as the other longer items cannot be read.
Is it possible to set the default field width to the widest item in the list, rather than the default?