Fitted cost sketch

What the number is

The sketch starts at a base, then adds an allowance per kilowatt-hour and per kilowatt of panels, then a labour factor. London-weight jobs can use about 1.14. It is priced as if the temporary 0% residential rate still applies.

It leaves out scaffold, a long cable, parking, a DNO export limit and making good. Read what a sane quote contains before you treat two totals as the same job.