Lack of visible supplementary Bonding

Hi Guys.   I looked a a job today with a 16th edition CU so no rcd on the bathroom lights.  There is no visible supplementary bonding. Lots of pipes boxed in, bath panel not removable.  I had a reading of pretty much zero ohms from the hot and cold below the sink to the radiator so suspect it is done somewhere.  However i suspect the lights are not done as i dropped the down lights out and the switch.   There is a class one shaver point over the sink although it doesn't have any exposed metal parts.  I am getting 0.25 ohms from the earth at the shaver to the sink pipes.  The bathroom is next to the CU, well it's outside the door so the cpc run is pretty short.  What sort of reading do i need to be seeing here before i don't need to worry about a supplementary bond.  Is 0.25 low enough.

Thanks

Gary