WTF was up with FGW & Heathrow Connect services this morning?

Apart from the delays, At Hayes & Harlington we were advised that the
10:15 up was going to arrive on the main line up platform rather than
the usual relief. So we all dutifully trooped over the new bridge to
P2.

Various trains came through following very odd announcements over the
PA, implying that certain trains would stop (and they didn't).

Then came an announcement that the next train to arrive at P4 was a
Heathrow Connect train stopping at every station to Paddington. So,
we all traipsed back over the rickety rackety bridge again to P4.

Yet another daft announcement followed quoting yet another departure
time and a FGW train pulled in - stuffed to the gunwhales. Nobody
actually applauded when it arrived, but it was a near thing. It
turned out to be a 'fast' train but proceeded at a rather leisurely
speed.

(Fortunately, the return trip was better. It came up to expectations
but not hopes.)

I know that these things are beyond any control but I'd sort of like
to know WTF was going on.

Regards
JonH