Unless there’s another by-election which UKIP have a chance of winning in the next ten months or so the next opportunity for Nigel Farage’s party is the elections next year.
Firstly, the referendum on EU membership could be held late next year. Of course that will be crucial for UKIP if they want to keep building momentum but with a date yet to be set little can be said on the matter, other than that the referendum will energise the party’s supporters and could be used to persuade 'no' voters which don't support UKIP to end up supporting UKIP.
Welsh Assembly Elections
In the 2011 elections UKIP failed to win a single seat in the Assembly, but in 2015 UKIP won 13.6% of the vote in Wales - a total actually higher than the UK-wide share for the party. To keep their momentum going the party will need to get similar vote shares across Wales next year and even gain a couple of seats, something possible under the proportional elements of the Welsh voting system. In Wales, the party could make a breakthrough.
UKIP struggle in Scotland. The party failed to scrape even 2% of the vote north of the border in this year’s general election. But the party did win an MEP in 2014 (one out of six) albeit on a low turnout. UKIP support in Scotland is small and spread out, but with the proportional element in Scotland’s voting system UKIP have a higher chance than in a first-past-the-post election. UKIP’s chances are much slimmer north of the border than in the Welsh elections, but in terms of vote share the party could make some progress. Progress in terms of vote share could show that they are improving in Scotland, something which could help them significantly.
English Council Elections
In these elections UKIP will need to hold onto the seats it currently has and gain new ones too. This will help the party in the long run as it will allow them to build and strengthen local bases, which will be key in future elections.
It looks like UKIP will have a future in British politics. 13% of the vote in a general election is not something that will disappear. But with just one MP in the House Of Commons the elections (and potential referendum) of next year can help cement the party's place as the UK's third party.