Shed you're not getting that one. Any LHR R3 impacts direct non stop long haul out of MAN, it's not something that can be viewed in isolation. As MAN already has an existing long haul portfolio where growth going west may well be slowed due to existing LHR/MAN operators getting to grips with a changed trading environment, where the market share position on LHR-US would be impacted almost overnight with a 50% capacity change at LHR. That would likely concentrate minds on London for a while until things panned out. You can bet DY would have a go at LHR, another reason LGW/GIP are desperate to stop R3 lest EZY take the chance.
Oddly enough LBA wants R3 as it would make their connections to London and beyond likely safer, the government also has the option to ring fence further new slots to be used only for British Isles airports currently unserved.
If LPL got a LHR link again that would further impact MAN as would further growth on LBA-LHR as both are in MAN's catchment area. Your argument this is simply a matter of another runway in the SE is not borne out when you take a look at the wider picture.
InOban, um not really. Backtracking all the way to AMS is often not as attractive as a T5-T5 transfer, especially on the way back. AMS remains a good option but BA still has a huge amount of connecting traffic out of GLA/EDI/BHD/ABZ.