I moved out about 5-6 years ago, when I was around 20-21.
Money wise for you mate - would be cheaper to pay your mum... As for them £425pm you looking at another around £100 of council tax, gas/water/electricity - if you good you might get away with just another £100 for them 3 per month (as place is small, so you use less heating etc), then you need things like TV licence, Internet etc etc! I rent a 1 bed flat at the moment - it's £525pcm...with bills it's around £750pcm
But at other end of stick - it's freedom if you rent your own place! You can do whatever you like, have anyone around etc etc!
Try looking in local newspapers for private lettings mate... That usually cheaper! I found one(well, my mrs did) and we moving in October to same size property that we are now, but with drive and garden for £500pcm incl all bills.
I found few places like that - when people build a small extensions to their house and then rent it out to pay for their mortgage...yea, you will be close to actual owners so you can't really have 24/7 parties... But you still have your own entrance etc - so it's basically classed as different building/house. Worth a look! Good luck mate! It's pain in the arse and not cheap