Replacing Flat roof with Piched roof - validate estimate

Hi

I would like to validate an estimate I have receive to replace an existing flat roof with a 45 degree pitched roof. The details are as follows:

Size of existing flat roof = 7310mm (length) * 2730mm

New pitched roof with Tegral slates, insulated , fascia, soffits, gutters.
4 Velux windows - 780 * 1400

How much should I expect to pay for this? Would 15,826 + VAT seem over the top?
Thanks for your help

How does the price compare with the other estimates which I am sure you will have obtained?

I am waiting for a second estimate, and they are dragging their feet.

I asked, as I would like hear other people's experience of these costs.

the velux cost about 3-350 each plus maybe another 3k for the other bits
say 5k for the lot
for 2 carpenters
demolish existing roof - 1 day
build new roof frame 1-2 days
fix slates 1 day
fit and flash 4 velux windows - 2 days

misc stuff - gutters etc 3 days
plastering 2 days
roughly 11 days * 2 workers = 11k+vat. not exactly cheap

Don't forget to add in preliminaries like insurances, scaffolding, removal and disposal of old roof materials etc and add for profit (+5% anyway). Is there any wiring included (new ceiling lights, associated switching?), is internal decoration included? If it's being done by a properly insured and registered building contractor it sounds about right, but not cheap I guess.

Thanks everyone

The builders have provided separate estimates for wiring, electrical, preliminaries, insurance and sitworks. So the 15,826 is just for the actual roof...