I invested in a cross trainer last year, RRP about £500 but I got it for £360 on Amazon. Which is the same as a year's gym membership at £30 a month, but of course I've still got my machine! I love it and much prefer it to my exercise vids because I can put my headphones on and listen to audiobooks, so far I've got through a couple of Dickens and an Ian McEwan, improving my mind as well as my body! They also work as a distraction so I'm not watching the clock all the time, the time goes by that little bit easier and I don't get bored.
So yeah I would recommend getting a treadmill or a cross trainer.