I think it's very worrying, although it's difficult to know what influence UKIP will have after leaving the EU, when their whole reason for existence will have gone.
The Labour Party has always been a broad church. Although its roots are in the trade unions, it's always had wide support from intellectual socialists with various beliefs. New Labour 'Blairites' have complicated the picture. Somehow or other the various branches need to start working together, but I'm not sure that's possible any more.
With talk of a new centre party, the danger is that the Conservatives will have a permanent majority, because the opposition would be split.
I doubt if there's much chance that UKIP will ever form a government. Firstly, they're always squabbling and secondly, I think the liberal (with a small 'l') voters would come out in force to defeat them. Nevertheless, they will influence the major parties, as they did with the call for a referendum, and could let in Conservatives by default if the opposition is split.