Heating/hot water for a garden lodge

[John the hippy]

Hello,
wonder is someone could give me some advice?
We're building a wooden garden lodge for my mum-in-law in our garden.
Its about 11m x 5m in size, with a bedroom 3x5, main living room/kitchen 5x6, and bathroom 2x2, with a separate utility room of about 2x1.5
We were talking to the company Keops who are building it regarding heating using electricty.
They suggested a 2kw heater in the bedroom, 2 x 2kw in the main room and a heater/towel rail in the bath room.
We will have a 63amp fuse from the main house feeding the building via an armored cable.
My question is regarding the options for water heating?
Piped gas is not an option, and we're not keen on the idea of gas bottles ( but might be persuaded)

The lodge is about 40 meters from our house, so we cant spur off the water from our property.

Would a electric water heater work for a bath/shower/kitchen use, would the flow be enough?
Or would a unvented pressurized hot water tank heater with immersions heaters be a better option.
We don't have economy 7 electrical supply.

If we thought about the idea of gas bottles, what would the saving be, say over a year?
How long would the bottles last, on average, saving if she had a bath/shower once a day.

Any suggestion would be much appreciated.

 

[flameport]

Unvented cylinder with immersion heater, assuming the water pressure/flow is suitable for it.

Instantaneous electric water heaters will provide a feeble flow rate (so forget about a bath), and very likely require a much larger electricity supply.

 

[dilalio]

Building control will need to be involved.

 

[vxxbcks]

How about an air source heat pump. You might even be able to get RHI support on it.