using 2 x 1.8kg lager kits to make 40 pints /no brewing sugar?

[ogden25uk]

if i bought 2 of the bog standard 40 pint lager or bitter kits and just used the 2 syrups to make just one 40 pint batch of lager. would that be possible, and would i use sugar for primary fermentation or not? would this vastly improve the taste of my beer. i'm a beginner eager to improve the taste of my lager/bitter etc. also would it be possible to mix , say a lager kit and a bitter kit or a lager and cerveza style kit? any help would me much appreciated