I've just gone through the same pain at carpetrite. They wanted to charge for everything and it ended up costing sill money. In the end I got two mobile independants from the Yellow Pages to come and price up and they too were about the same price. Their only bonus was that I would be getting MUCH better underlay from them which improves the wear and feel of the carpet.
So, I bought the carpet from Carpetrite and fitting at £2.50 per sq/m. Bought some Cloud Nine underlay and gripper rods (recommeded by both independants) from Ebay at about £3 sq/m (carpetrite wanted about £8 for their basic stuff). And hey presto, fitted for not too much extra work and lots of money still in my pocket to buy bike stuff!!