The ATOC London Connections map, alongside the London & South East map
and others are available online in PDF format from the National Rail
website at...
http://www.nationalrail.co.uk/maps.htm
...though it would appear that the new London Connections map has not
yet been made available online, the one on the site being dated January
2005.
I have just looked at the london connections map on the page and it
does contain heathrow connect.
Indeed. The page has now been updated with the new map.