Complex sentence: Toleman acquired major sponsorship in 1985 from Benetton, who had previously sponsored Tyrrell and Alfa Romeo; the knitwear firm bought them over the 1985/6 close season and were renamed Benetton Formula Ltd for 1986.
Split into simpler sentences: Toleman acquired major sponsorship in 1985 from the Benetton clothing company, which had previously sponsored Tyrrell and Alfa Romeo. During the 1985/86 off-season, the knitwear firm purchased the team and it was renamed Benetton Formula Ltd for 1986.