In message
of
Mon, 18 Feb 2008 14:53:14 in uk.transport.london, Mizter T
writes

[snip]

Sorry for the extra long post, I guess this just goes to prove that
life is complicated! If you've got any other questions, or if the
above is about as clear as mud, then please feel free to ask away.

Your long post omitted to mention the service I use when I must use
Heathrow and can choose the mode - Heathrow Connect (HC)
http://www.heathrowconnect.com/.
30 minute service interval and about 30 minutes travel time.
Roughly half as expensive as Heathrow Express (HE) which has double the
service interval and half the travel time.
Roughly double the cost of London Underground and half the travel time.
I have never known HC packed (I await screams telling when it is so .

I don't recall the signage at Heathrow but HC leaves from the HE
platform. Follow signs for that service. The OP should make sure not to
take HE or a courteous ticket inspector will take loads a money.
--
Walter Briscoe