i got one of these the other day £15 pretty basic but for the price i cant moan kinda cool for the 360 vids you can find. though no built in control so you have to pre load the stuff before you put the phone inside it, or use an external controller
I did some research and the best of the budget ones seem to be the BOBOVR Z4 and Virtoba X5.
If you've got your own headphones (I've got some Sennheisers) then you can get the Virtoba X5 Elite for £16.99 from Amazon.