While FPTP is responsible for its own share of distortions, in this case it's the use of Single Member Electorates that was the primary cause of UKIPs poor seat-for-vote return.

For example, something very similar happened in the last Australian Federal election, which doesn't use FPTP (it uses full preferential voting) but does also use Single Member Electorates: The Greens got 1,385,650 first preference votes, also making them the third-biggest party, for the return of 1 seat (out of 150).