@ Mr Mac
All fine and dandy for you. I periodically visit relatives in Germany and I find that it is cheaper to fly from Heathrow with BA rather than fly from my local airport of Bristol.
Once the rail link from the west direct to Heathrow is in place it will be even easier for me to get the Heathrow. No more sodding coaches from Reading.
I believe the rail link will also make it far easier to access Heathrow from the north. Not only that but
AFAIK the rail link is due to take place regardless of any decision on a third runway.