To respond to human need by loving service.
Christians and Christian organisations have a long history of providing caring services to people in the UK. Even in a country as rich as ours, there are still many people who are in need of a helping hand in one way or another. The Christian response is varied and creative, ranging from night shelters and soup runs to help the homeless, to Street Pastors showing care and support for the crowds of young people in city centres late at night.
This aspect of mission impinges more on the political sphere than the two previous ones, and governments are able both to discourage and encourage christians taking an active role in this area.
For the most part, no government of whatever party is going to go out of its way to discourage Christians (or anyone else) from serving the community. If churches want to provide, for free, services which the government would otherwise have to pay for, they are welcome to do so. However, some legislation can have the unintended consequence of making it difficult for Christians to carry on serving people.
The current government passed legislation which apparently made it obligatory for Catholic adoption agencies to place children with gay couples, despite the agencies disapproval of homosexuality. Whether the Catholic agencies helped gay couples or not was not really an issue as there are plenty of other agencies that would do so. However, for the agencies, it meant being forced to act against their consciences and most agreed that they would shut down (causing regrettable suffering for children) rather than betray their beliefs. In the end, a court ruled that as long as there were ample opportunities else where to serve the gay community, the Catholic agencies could continue as they were. None of the parties have openly said that they would push forward legislation that would make it difficult for Christian churches and others to carry out their mission, but it would not surprise me if cases like that of the adoption agencies became more frequent.
The other issue which is of interest is the extent to which the different parties will encourage Christians to get involved in their communities and help out. I seem to recall that at different times all of the parties have spoken up on this, but there seems to be nothing in any of the manifestos, so we will have to wait and see.