Impossible to price without seeing it imho.  Is this in an empty house or is it in a house where you all live with carpets, furniture, budgie cage etc etc etc?

How many rooms does this 950sf include?

Hall/stairwell/landing?

Is there coving?

What about existing lighting, is it to stay?  If so can it be 'lowered' onto the new ceiling?

My first thought though is why do you need to fireproof all the ceilings to this standard?

depending who you get, between £1800 to £2800 labour only (+ vat possibly too)

I was calculating on what my spread charges me.  The two of them charge £450 a day labour (together) and I reckon this job was 4 - 5 days.  Don't forget the clearing up on a job like this, all wall splashes have to be removed (or walls protected) etc.  Not as straightforward as a new build.

This may seem high but that's what we have to pay around these here parts  

I had a customer on the phone a while back trying to get quotes for a new kitchen floor screed (new extension).  Room was 12' x 12'.  Best labour only price she'd had was £800!  Not bad for half a day!

I also find that trades such as plasterers see a 'one-off' job such as this, as a chance to earn a few bob as they're never likely to get any more work there.  They price work differently for builders as they want repeat work.  Might seem unfair but that's how it is.  

Jerry is of course right and if the spreads are busy a one off will be priced higher, if the demand is high the price will follw accordingly. That said I did a house back in January overboard two bedrooms ceilings, one landing and one bathroom ...tape and skim. Skim over artex of kitchen/ diner and sitting room started monday had friday off job done cost 1800 euro including materials that was a nice earner for four days for me seeing as it was the bad month of torrential rain, (inside work being welcome).............One of the reasons I left the U.K was because the plasterers were the worst paid of all the trades on site back then, how things have changed.