I've tried to unlock a VCR using a universal remote that ran through all the codes (automatically) for all VCRs and finally it stopped on the correct one but nothing on the universal remote would unlock the VCR from 'child lock'.
I would suggest buying a universal remote that has a 'child lock' function on it and then run through all codes until you get to the correct code for your TV.
The memory where the detail of the settings for everything (channels, child lock etc.) is in an EEPROM, (Flash Ram) so even leaving the power off for a long time won't help, and unplugging the Flash Ram won't help either as the data (including child lock) is still in the Flash Ram. You could replace the Flash Ram with a new IC which will be blank and the child lock should be off.
The final method is to get the original remote, but some TVs/VCRs have codes to enter prior to unlocking the TV/VCR.
Also, the Flash Ram is often a plug-in chip that plugs into a small socket and sometimes the number will start with 24xxxxx.
Phone up the company that sells the product and ask them what to do, but they will ask for the serial and model numbers of the TV/fridge.