Corbyn and Heathrow
A couple of points on this:
(1) The outcome of a Parliamentary vote on Heathrow expansion would be determined by one thing: the number of Labour MPs in favour (and willing to vote in favour irrespective of any instructions from the whips) has to be greater than the number of Conservative MPs against, after abstentions and non-attendances are taken into account.
(2) It is unlikely that the SNP group has a homogeneous view on Heathrow expansion, many of them want it badly.
(3) If the mathematics in (1) above work in the government's favour, it doesn't matter how the SNP vote.
(4) If not, there may not be a parliamentary vote at all, and the noise of cans being kicked down the road will be deafening (louder than any aircraft on the flightpath) as another Commission is set up with a remit to look at Heathrow only and told to report after the 2020 election;
(5) Corbyn has been a serial rebel for 32 years, this will make it very difficult for him to be able to enforce his will on the Parliamentary Labour party already split down the middle. Most Labour MPs realise that it's very unlikely that they can win in 2020, so many may think nothing of the rebelling. Some may do it in the hope of bringing down the Corbyn leadership. In many ways it could be reminiscent of Iain Duncan-Smith's ill-fated Conservative opposition: the serial rebel turned leader or, if you prefer, poacher turned gamekeeper.
Either way, it is far too early to tell how things will pan out, it could go any number of ways. For the Labour leadership to do a U-turn on this would upset many of their MPs. What would be the effect of Labour voting with the Greens, the SNP and the Libdems (remember them?). On this issue, it wouldn't look good.
One thing is for sure, the 50 year saga looks like not being resolved any time soon.
Hope this helps.