The reason fares are high ex LHR is that Heathrow is full and competition constrained.
BA draws the majority of their UK passengers from a relatively small geographic area around LHR which just happens to also be the most affluent in Western Europe.
Out with the M25, and certainly north of Birmingham / Manchester BA have almost no market share having abandoned the English regions, Scotland and Northern Ireland to others a long time ago
Capacity to Scotland / English regions is predominantly point to point, and as I have noted just this week fares undercut rail by some margin. When did we ever think that would happen? EDI LON in 4.5 hours is highly competitive with air, in terms of time; with the result BA have to undercut fares.
Having abandoned the UK in favour of London, (evidenced by complete lack of national advertising campaign for at last 3 years) BA has to use the capacity they have to from Europe to fill those seats that would otherwise go begging. This supports both their long haul operations and the point to point traffic to Europe. However they have to compete against major players who do not operate at capacity constrained airports and who in turn have to compete with Asian and Middle East carriers and the associated service levels they offer. As a result you see fares at levels they should be at here. You also see deals the like of which simply do not happen here such as Silver cards for 1 flight and mileage deals that far outstrip anything ever offered inn the UK. The same holds for the USA though there the deals tend be miles for credit cards in the hope BA can lift their profile.
So it is supply and demand, but it is also artificial in that runway capacity, if improved would almost certainly bring greater competition and thus lower fares. Alliances have also not helped fares, they do allow for costs control and perhaps better integration of services but they do nothing for fares especially in F/J. Add to this mix the use by BA of 777 for long haul and in the near future Dream liner. The use of these aircraft also limits capacity particularly in M and WT+ but also to some extent in business (versus an A380 for example) and in turn allows BA to price more aggressively.
It is not a situation that will alter any time soon and as a result forces passengers like me who are price sensitive premium travellers to look elsewhere. I have been a fan of BA for 25 years but the last 3 years have seen such a decline in service standards and such an increase in fare levels that they no longer offer value for money, from the UK. I have become a Euro cheat and a EU departure passenger as I wished to retain both status and miles. The latter is no longer a draw for me as the redemption opportunities have been very seriously eroded in the last 3 years also.
As someone who travels predominantly now for leisure I am amazed that BA simply do not offer the sort of fares available ex Europe, ex the UK, but on a highly restricted basis. I know my flight to Hong Kong will have dozens of upgrades from M and WT+ to J and F both ex LHR and ex HKG in August. It happens every year and I have in the past benefited from it. Why then do they not offer better J class fares at the time of sale to what is clearly leisure traffic and who will take a flight on a specific date and time come hell of high water?
At the end of the day it is their business and I have to decide if I will travel with them. Currently there is no compelling reason to do so and they do not currently offer this passenger value for money.