It definitely needs checking, if you need unit changing it would be in the region of �200-�250 providing all the earthing is ok, if not this will also need upgrading, if you are not sure how to proceed, have the unit checked first then ask the sparky to do a "periodic report" for you, this will cost approx, �100-�150 and everything in the propety will be checked and he will explain what needs doing to bring the installtion up to current standards. most self employed sparkies are very honest so don't worry about being ripped off, go to napit,eca or nic websites and look for local registered electricians, just put in your postcode and it will bring up phone numbers and names for you, but please get it checked asap, good luck, Ray