Having lived in both (1910 terrace I bought, 2007 detached bought with DH), I love the room sizes and proportions, window sizes, storage, and the period features of the terrace.
I love the insulation of the new build.
Have you looked into how much insulation you have in the loft? Topping that up (from nothing
) made a massive difference to how quickly the house heated up, and how long it retained its heat.
I echo the comments up thread about floor length, lined curtains, and a door curtain.
Can you arrange the furniture to expose the radiators in the winter? we had a summer and winter arrangement of the sofas - summer, sensible conversation arrangement, hiding the radiator. Winter, less suitable for conversations / visitors, and difficult to draw the curtains, but one sofa cutting off the bay window. It was FREEZING behind there when I drew the curtains, but the radiator was exposed to the room!
Think my ideal would be a victorian, or maybe 1920/1930 detached which has been done up massively to put in the max insulation etc. Now, where is my lottery ticket 