The most frustrating thing is that when the external ambient air
temperature cools down (or at night), the internal air temp seems to
rise! :-(

The house is an 1800s end-terrace with (solid) walls, white-rendered
at the south-facing front, and it becomes incredibly hot during these
spells of hotter-than-normal weather. The 1st and 2nd floors are much
warmer than the ground - thankfully the basement remains at 20 deg or
below. The 2nd floor's pitched roof is insulated both under the felt
and above the ceiling joists.
I've tried covering a large section of the end wall with insulated
plasterboad but this doesn't seem to have made any difference.

Any ideas? Or does the large amount of solid brick wall mean that I'm
condemned to very slow changes in temp?
--
Mr B