Wooden panel yurt in South Australia

[Jafo]

Not sure how it works in the UK, but over here in the states, if you have access to the grid (electric mains) then what many people do is a grid tie system which basically works like this:

Your solar panels send power directly to the grid. This turns your usage meter in reverse. When you have no sun, like on cloudy days or at night, you use grid power as normal. The idea is to have your utility bill to be close to zero every month. This of course depends on how much sun your spot gets.

The advantages to this system is generally cost. With an off-grid system, you have to pay for the storage mechanism, which is generally in the form of batteries. This can be very expensive for even the smallest systems. With a grid-tie, the GRID is your battery and you only pay a small amount to tie into it initially.

The downside is, you are still relying on grid power, though I do understand there are some hybrid systems that allow you to store some on site (for emergency power) and pump the rest to the grid.

Over here, we have companies that will install the equipment free of charge, but you pay them for your power, at a much reduced rate. This is also dependent on whether or not your location is an ideal candidate. The company maintains the panels and equipment, you just pay for power. I never cared much for that option, but thought I would mention it.

You may want to consider some wind power for preheating water and also possibly pumping it, since I see you may be using holding tanks.