Ripped off?

[Vikkiog]

Hey guys, so my parents surprised me with a juwel rio 300 second hand for £225 my 21st as Ive been meaning to upgrade from my 180 for a while.
First off the measurements of the tank match the rio240 not 300 and when I phoned the seller he refused to believe me and wouldn't refund any money and since then I've been unable to contact him and as he delivered the tank to my parents I don't know where he lives. So firstly they've paid 200 for a tank and stand that costs around 400 new -.-
Next one of the clips on the impeller cover of the filter snapped off, it still holds on but is starting to get noisier. Now the heater is playing up, heating the water to 30 Celsius no matter what temp the thermostat is set to.
Lastly, the inside of the tank stinks! It smells of plastic or paint or something.
Now what I'm asking you guys is should I just keep it, buy new stuff for it and hope for the best or sell it on without the heater? Either way ill be losing money I guess. It's just driving me nuts as my parents thought they were being really helpful and the guy who sold it to them won't even pick up the phone.
Got a little rant-y there but thanks for any advice guys!

And just to add he delivered the filter first so I knew it had a broken part but that would only cost around £5 to get a new impeller cover.