Another earthy question

I've replaced the kitchen in a studio flat and I'm about to start on the bathroom. The original setup was that the hot and cold were cross-bonded under the kitchen sink and under the bathroom basin, the system was mainly copper and the kitchen taps were attached to the s/s sink. It now has a s/s hob and oven on the units on one side and, within easy reach, a s/s sink on the other. The electrical earth to the hob & oven is presumably connected to their casings. The monobloc tap is attached to the worktop and not the sink. The sink waste is all plastic. There is a small electric water heater under the sink supplying the sink and bathroom basin and it runs off 6mm t&e cable from a separate fuse in the consumer unit. The cu is probably 10 years old and has fuses and not rcds/mcbs. The cold water to the sink and water heater, and the hot supply from heater to sink and bathroom are in 15mm copper but with mainly plastic pushfit fittings, so no electrical continuity under the sink but pipes from under the sink to the bathroom are all copper afaict. As the hob/oven, sink and tap are the most likely items to be touched together I'd have thought that they should ideally be at the same potential so I wondered whether I should connect the sink and tap to the electrical earth of the water heater and continue this bond to the larger sections of copper pipework under the sink. The cold feed and the hot supply to the bathroom are isolated from this lot so I wondered whether I should just bond them together as they come up under the sink and bond together the hot and cold under the bathroom basin. I assume 4mm earth cable will suffice. I don't really want to replace the consumer unit at this time. I'd very much appreciate the help and advice of the experts in this group before I do any more.
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No replies yet. I suppose my question was just too long..... :(
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Don't bother doing supplementary bonding in a kitchen. Some people think it reduces safety. It certainly isn't required by regulations, unless you install a shower or bath in there!
Christian.
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