Labour do well and are able to form a minority government
If the Conservatives do badly, falling well short of their winning line of 323 seats and Labour do well, achieving say 280 seats or more, then they would look to form a minority government drawing on support from the minor parties to build the majority necessary to pass legislation.
The first priority would be to delay the 31 January Brexit deadline, meaning a request to the EU for another extension, which we can expect them to grant, however wearily. This would be followed by Labour negotiating a new deal and then a further Brexit referendum.
Meanwhile on the domestic front, the minority Corbyn-led government would have to negotiate support for its legislative agenda. The manifestos and political positioning of the minor parties are certainly more aligned to Labour than to the Conservatives (with whom quite possibly no one would want to do a deal); however Labour will still have their work cut out to govern effectively. They’ll have to negotiate over support for their more controversial policies, such as the nationalisation programme and the Inclusive Ownership Fund concept. This is not to say these policies won’t be introduced, just that they’ll have to make concessions to get them through. Undoubtedly the SNP would look for another Scottish Referendum and probably a review of the Barnett formula which controls the amount of public expenditure allocated to Scotland.
Labour have confirmed their intention to hold their first Budget on 5th February, which in theory means investors would have a few weeks to make any adjustments to their finances they feel appropriate following the formation of the Labour government.
Labour exceed expectations and win an outright majority
Like an outright Conservative majority, this would bring greater clarity on the future course of events. A delay to Brexit would be requested, pending further negotiation, followed by another referendum on whether to support Labour’s Brexit deal, or revoke article 50.
They would hold their Budget on 5th February, which would set the ball rolling on Labour’s radical manifesto to transform Britain.