Did my own after following a couple of threads on here with no electrical background/knowledge. I certainly wouldn't attempt a house rewire like yourself.
Mine was a simple configuration using a grid tie inverter that simply plugs into an existing socket, as i saw others doing on this forum and guessed it was something i could manage (shout outs to @Crossy and @BritManToo )
I too have old style spinning meter and export "unofficially" to the grid during the day. This is also why i only went to cover 50-60% of usage to avoid getting switched to new style meter, and maybe increase capacity after this set up has paid for itself.
Set up is coming up to two years and still on course to have paid for itself within my three year target, even with having changed one grid tie inverter.
Obviously when the grid goes down, so does our power so your second bird wont be killed but whilst you still have old spinning meter, it will certainly help bring your bills down and after R.O.I you will already have some infrastructure for your proposed set up bought and paid for before the more costly expense of a hybrid system