I don't think you're going to get a decent indoor cage for under £60.00. I got my indoor cage from Zooplus, and it's got a pen attached and another cage that I already had so my two have a big cage to share - the cage and pen came to around £80.00, though the same cage now has gone up to £99.00.
A lot of people on here use NIC cubes to make an indoor pen and then use carriers or box for somewhere the bun can go in. Or a dog crate with attached pen which you may be able to get cheaper than a cage.