I ended up with a 8.2kw DIY install with a 5kw hybrid inverter with 10KW battery storage. This is also with a G98 and a G99.
This enabled me to get a 5kw export rate from the DNO and for which I am being paid for by Octopus. Exported a tenner worth of electric already this year and Jan's a pretty poor month.
Whole system payback is looking at 48months. Cost me £8.5K, over double that for someone else to do it.
Took me about 8 months in staged builds and permissions but its certainly achievable.
I would plan out your systems, starting with say the small garage roof only...Apply for a G98 buy with a 5 kw hybrid inverter. That way they will allow it , and as you build more on later (time and money permitting), its just an add on of panels.
Contact your local council and ask for a "building compliance cert" for your work. Also make sure you obtain full electrical test certificate from your sparky for your solar...will need these later for octopus energy export payments and also handy if ever selling property.
Make sure you use full industry accepted components.. even down to roof hooks and rails. Easy to start up a wholesale trade account to obtain best prices.
Make sure your intended inverter and batteries are compatible, I would hold off on the battery purchases for a bit as prices about to drop a lot more.. Also batteries that can be expanded like pylontec.
My initial install didn't have the batteries, hybrids don't need them, and in my case funding money was coming in in dribs and drabs. Can add them later and be aware they can limit permissions from the DNO.
I just upgraded my G98 to a G99 later on, and with some additional electrical safety checks (which is a requirement for higher export limits on the G99 fast track), found it pretty straight forward.
I found a tower sufficient but had to move it several times, also they are in expensive and reusable.
U tube invaluable, for inverter set up training sessions and connections. Worth following it to the letter. Also tips on installation.
Fit bird netting to any higher arrays...use the black plastic coated wire, and steel fixings..not the plastic ones which dont last.
Found taking a long time to complete very enjoyable and easily one of the best projects I have ever done.