In much of Europe tank heaters are at least as rare as the copper finned water-tube boiler "tankless" type heaters are here. (I can't recall having seen any tank-type water heaters in the Netherlands when I lived there. Most homes there had two water heaters, one for the bath/laundry, and a smaller one for the kitchen. ) I'm not sure what the relative distribution is in the UK.
So are your hot water cylinders (tanks) not made from copper? They are here and europe or Stainless steel. In Germany now the move is away from Copper altogether towards stainless steel tanks and pipework or plastic pipework.
Having the two heaters makes sense for short draw hot water demand at the sink, or electric under sink 15litre heaters currently subject to boiler location you can get long draws before hot water hits the tap, resulting in cold water hand washes.
Generally you'll find apartments and such high density housing have tankless systems installed. Some like in Poland that I have seen are on a form of district heating. In Germany I couldn't tell you the proportion but anyone with a basement will have at least a 500litre storage tank if not 750 to 1000litre. This will be supplied with solar and gas/oil/wood/pellet fired boiler.
In the UK it was traditionally a tank and separate boiler, the system was generally open vented(ie atmospheric pressure not sealed) but from the late 70's combi boilers were introduced (I believe by Vaillant group) House builders took to them with relish as it freed up space in the house and cut down on installation time. Therefore a majority of houses are fitted with combination boilers, but not all some are still fitted with a system boiler and cylinder(tank). There are even some combination cylinders with inbuilt condensing boilers pressurised hot water to supply higher flow rates for power style showers.
With current building regs here The latest round of Part L here is a further drop of 25% in energy usage on new build but not legacy(grandfathered) build. Moving towards 2016 when all new build property has to be low energy carbon neutral. I think we are looking at space heating requirements of 4kW heat input.