I suspect that, across the last three decades, many of the Eastbound routes have been plundered by the main Euro hubs (AMS, FRA, CDG, MUC) being able to collect from the UK regions and then the vast expansion of the ME carriers. Westbound? Perhaps not as strong but, again, the demand of regional feeds to LHR for transit have all but gone. A number of smaller carriers such as Icelandair have found a way to link from LHR but (again) also from the regions.
I've just looked down the list of carriers currently at LGW and some names I have never heard of. The combination of new short, medium and long haul competition has been relentless. Always the problem for a company that has been top of the heap - everyone will want a piece and there are many pieces to be had. Also, as we all know, old companies can be slow to see the changes - not just in aviation but in every field of commerce and govt.