The band’s name seems to be spelt usually as In-Betweens with a hyphen, or as In Betweens, but on their singles it appears as one word, Inbetweens. See label shots at 45Cat.com.
Single on Impact by Dunedin band formed 1967 when its members were still at high school.
For more details see Boom Sha La La Lo (1970) their other charting single.
Caution Googler! Clem Curtis & The Foundations issued a single in 1976 with the A-side/B-side titles Make A Wish/Amanda.
Vanity Fair's Early In The Morning (1969, #8 UK, #12 USA) was another Leander-Seago composition. Mike Leander (1941-1996) was a major producer, composer and musician in 60s and 70s Britain, known for his work with numerous big names including Engelbert Humperdinck, Cliff Richard and New Zealander John Rowles (see, for example, his hit If I Only Had Time).
Friendly Persuasion was an early project by Mike Leander's protégé Gary Glitter (Paul Gladd). Mike Leander wrote Glitter's hits and played most of the instruments on the recordings.