that is absolutley shocking, £1100.
i'v just priced a living room, kitchen & bedroom re-skim few bits of bonding to patch first and went in at £800.00.
im gob-smacked you didn't question the point of him making so much in 1.5 days, i would make him rip it down, do it properly and throw the kitchen on too for what you have paid.
staggering ceiling boards is rule No. 1, its schoolboy stuff.
i dont think i would ever skim over paper tape either.
i think you should have been looking to pay around the £600 - £700 inc mats + a lab for ceiling help. off the top of my head before i get jumped on. but i suppose its where you are in the country, south yorkshire (where im from) is the plastering capital of england so you have to be quite competitive with the pricing in comparison to somewhere like the south-west of england.
hope you get it sorted, Mac