Radio-Controlled Clock Behaving Oddly

[MJWSurrey]

For what it's worth, mine suddenly stopped working, after a battery change, never moving off 4, 8 or 12.00, despite several resets with different batteries.
Encouraged by this thread, I took it up in to the loft, reset it beside a Velux window, for as clear a signal as possible. It is now fine again.