The NON ISOFIX 0+ seat is £180 including VAT, the ISOFIX is £280.
To charge £200 to turn off the airbag is, I agree, disgusting. I guess they are thinking short term profit over long term happy customer?
What would they then charge you to switch it back on later? £400 in total?!
But anyway, the price is £180 for non-isofix, hope that helps.