The firm said it would be working closely with the Vauxhall sales team to provide any benefits of joint fleet deals, while it will also use its own fleet specialists, backed by a 90-site dealership network.
Stronger residual values are being targeted by an approved used car programme, being introduced this year.
The new Nubira launches in the UK in September as a saloon, with a hatchback variant arriving in 2004.
The firm says pricing will be in line with GM Daewoo's competitive approach. It will be offered with a 1.6 and 1.8-litre petrol engine, along with a five-speed manual gearbox and a four-speed automatic.
Other changes to the line-up include a more powerful engine for the 1.0-litre Matiz, offering 64bhp, while the Tacuma will get 1.2 and 1.4-litre petrol engines from April. With the backing of GM, the firm is planning a new sports utility vehicle for 2005 and a full-sized MPV is also expected.
LPG will also be offered, with a 1.0-litre unit planned for the Matiz alongside clean fuel versions of the Tacuma and Nubira. Total sales for Daewoo were 14,000 during 2002, but under GM this is expected to grow after this year.