Answer by taking a quote from the following article:

Echo & the Bunnymen are an English rock band formed in Liverpool in 1978. The original line-up consisted of vocalist Ian McCulloch, guitarist Will Sergeant and bassist Les Pattinson, supplemented by a drum machine. By 1980, Pete de Freitas joined as the band's drummer. Their 1980 debut album, Crocodiles, went into the top 20 of the UK Albums Chart.

In June 1982, the Bunnymen achieved their first significant UK hit single with "The Back of Love" (No. 19). In July 1982, they performed at the first WOMAD festival. This was followed in early 1983 with their first Top 10, the more radio-friendly "The Cutter", which climbed to No. 8. The parent album, Porcupine, hit No. 2 in the album chart. Now firmly established as a chart act, further hits followed with a one-off single, "Never Stop" (No. 15), and "The Killing Moon", a preview from the new album featuring a dramatic McCulloch vocal, which became the band's second UK Top 10 single at No. 9.  Following a PR campaign which proclaimed it "the greatest album ever made" according to McCulloch, 1984's Ocean Rain reached No. 4, and today is widely regarded as the band's landmark album. Single extracts "Silver" (UK No. 30) and "Seven Seas" (UK No. 16) consolidated the album's continued commercial success. In the same year, McCulloch had a minor solo hit with his cover version of "September Song".  Echo & the Bunnymen toured Scandinavia in April 1985, performing cover versions of songs from Television, the Rolling Stones, Talking Heads and The Doors. Recordings from the tour emerged as the semi-bootleg On Strike. Unfortunately for the band, Ocean Rain proved to be a difficult album to follow up, and they could only re-emerge in 1985 with a single, "Bring on the Dancing Horses" (UK No. 21), and a compilation album, Songs to Learn & Sing, which made No. 6 in the UK album chart. However, all was not well in the Bunnymen camp, and Pete de Freitas left the band. Their next album, the self-titled Echo & the Bunnymen (1987), was initially recorded with ex-ABC drummer David Palmer, but when de Freitas returned in 1986, it was largely re-recorded. Eventually released in mid-1987, the record sold well (UK No. 4), and was a small American hit, their only LP to have significant sales there.  In the United States, the band's best-known songs were "The Killing Moon" and "Lips Like Sugar". "Bring on the Dancing Horses" is well known as one of the songs on the soundtrack to the John Hughes film Pretty in Pink. "The Killing Moon" was featured in the films Grosse Pointe Blank and Donnie Darko, and in Series 2, Episode 5 of the E4 series Misfits. Ocean Rain's "Nocturnal Me" was used to close out Stranger Things Season 1, Episode 5. The band also contributed a cover version of The Doors song "People Are Strange" to The Lost Boys soundtrack.

When did they achieve their mainstream success?
1983