If you want a decent job done do NOT use these people.They are cowboys and then some.
Any faults are always the fault of the customer. One of our windows was put in without a lintel and when the cracks appeared, it was our fault for not asking for one! The draughts and whistling from all the windows wake us up at night as they are so noisy but all they do is send a guy (whose full time job, by his own admission, is dealing with complaints only)with a tube of sealant to go around and around with more sealant. They say the draughts are not really draughts, even though it will almost blow out a candle on the window ledge.
It is just the cold!!!Customer service does not exist in this company.