from a bar-room lawyer..you can change a child's name by deed poll and then have a new birth certificate issued in that name (ie: yours)if you adopt..that's how it was but easy to check with the relevent offices.
I'm sure it's all still available and I know deed poll stuff certainly is as I have a PI firm in Mayfair tracking a conman here who did so.
I think the only change may be the Govt now wants all this stuff on it's data base where it didn't previously and soon some DNA and then will probably want the kid chipped..although they may start with us oldies first if they are planning to produce Soylent Green to feed the country.