Having Jim Callaghan call the election in October 1978 is really the only way of keeping Labour in at this point. Problem is, the election is likely to result in a hung parliament, or at best a small majority. It may be hard therefore (given what happened OTL from 1979-1982) to keep Labour from being no-confidenced at some point, before the Falklands roles around.
Heath winning in 1974 could lead to a labour-dominated 80's, but that's before your desired pod.
I imagine the economy will struggle, much as it did IOTL, but without the Thatcher policies. Hopefully Labour won't have to ask the IMF for more cash.
I can see Callaghan (and whoever takes over from him, because he probably won't be around for the full parliament) having a solid, business-like relationship with Reagan, unless it's Michael Foot.
Not sure how the cold war goes here-you probably won't see any major reform until Gorby arrives on the scene and I'm not sure who'll be PM at that point, let alone Foreign Sec.