These new 'personal numbers' are also referred to as 'follow me' numbers.
The only reason I know about them is that I nearly phoned one recently, thinking it was related to legitimate business, but then realised that the prefix looked a bit odd and I wanted to find out what network it was attached to.
070 numbers are forwarded to real mobile or land line numbers, but can also be forwarded to premium rate numbers. This is where I don't get how the scam is possible, as I thought that the owner of the forwarded number got charged for the connection to the target number. That is certainly the case with my own 0845 number - I pay for the forwarded connection to my mobile.
God knows when these things were introduced, it was definitely done 'on the quiet'. The only reason I can see for allowing forwarded number charges to be passed on to the end user are fraud, and I reckon that OfCOM should stomp on that rather than requiring some pathetic warning.