Sigenergy setup

Hi Solar experts and enthusiasts!

I’ve had some quotes for a system in East Sussex, consisting of the following, and I’m not sure if it’s a good deal or not:

18 x 470w panels
Van der vaulk flat roof system
8kw sigenergy inverter
10kw sig battery
Sig backup gateway

£13,500

This is on two flat roofs. Tower scaffold only required and all cable routing is surface mounted on the outside.

Any thoughts?