Quote Check - 18 panel + battery system

This is a follow-up to this post: https://www.reddit.com/r/SolarUK/comments/1mk4v71/solar_panels_on_garage/

I have a final quote from The Solar Bureau (via Solar Together) for a system with 10 panels on the house and 8 on the garage. The battery and inverter are going in the garage too.

18 x Aiko Energy 445 Watt Panels (AIKO-A445-MAH54Mb)
1 x H1-6.0-E-G2 (Fox ESS)
1 x EP12 Plus(Fox ESS)
18 x TS4-A-O (Optimisers)

Standard System Price: £5,482.00
TIGO Optimiser: £990.00
Bird Mesh (BE): £630.00
Fox EP12 "H" Heated 11.52 kWh Battery - 10.37 kWh Usable Capacity: £2,502.00
Bespoke Scaffold: £1,700.00
7 m Trench: £750.00
Extended Cable Run: £850.00
Slate/plain tile installation: £350.00

Total System Price: £13,254.00

I've got gas central heating and only using 2314 kWh annually.
The system capacity is 8.01 kWp with an estimated annual output of 5,822 kWh
Estimated payback time is 11 years

Going to think about it over the weekend, but I'm planning to go for it.