U values for older houses ?

In a previous thread a discussion formed over the merits of new houses
over old, one obvious advantage being the greater thermal efficiency
of new houses.

The current building regs for the U value of external walls is 0.35.
My 1950's "ventilated brick cavity brick" is apprently 1.9.

Does anybody know what the likely U values would be for older houses
e.g. victorian houses with solid brick/stone walls, cottages with 2
foot thick stone walls etc.

TIA

Paul