I've decided to start work on a major rebalancing of pak128.Britain - see here: http://forum.simutrans.com/index.php?topic=11849.msg116481;topicseen#msg116481 (http://forum.simutrans.com/index.php?topic=11849.msg116481;topicseen#msg116481)
I'd be really grateful for advice from other standard pakset maintainers on how they go about getting balancing right.