He went back yesterday and sent this update.
Managed to get to Llanon again today, Thursday 8th, about 15.30, and saw two
adult birds flying about, hawking for insects. They occasionally approached the
nest as if they were trying to entice young birds out. No birds visible at the
rim of the nest, however, as often happens if the young are sufficiently well
feathered. One adult finally entered the nest after about twenty minutes and
appeared to feed young birds (a very brief glimpse of one small
head).
A late date certainly.
The nest is on house immediately past the very small triangular field with young bullocks on
the right (before you get to the vintage bus turn). I mention this in case
others passing can also keep an eye open.