Rear wheel sideways "play"

take the wheel out
...

i've been told that its better to have a little (and i mean very little) play than to have it to tight

wrong. as for bearings, tight it has to be. in case of cup and cone, where you set the tension, it has to be tight but not so much as in 'it makes you feel the balls through the axle' kind of thing. you'll notice once you try, but no play. once you got past that point, give it a tad more and try spinning the axle.

a bit loose is loose and will be much worse under load. a bearing with play rattles itself to death in no time.