Also depends on what you'll be cutting. Makita do a lovely battery powered circular saw which cuts up to 18mm, if you don't need a 40mm plunge saw then you can get a much nicer lightweight one that will cut 95% of what most people use a circular saw for.
Of course a track saw is what you really want to make the job a pleasure but you won't get that for £100.
Also depends on what you'll be cutting. Makita do a lovely battery powered circular saw which cuts up to 18mm, if you don't need a 40mm plunge saw then you can get a much nicer lightweight one that will cut 95% of what most people use a circular saw for.
Of course a track saw is what you really want to make the job a pleasure but you won't get that for £100.