It always works out cheaper if you buy 'roll ends'. These are pieces which vary in size but you will rarely find one that is big enough for a room more than 13ft wide, which is the standard width for carpet rolls.
There are numerous places which sell roll ends locally.
Two I have used in the past-
Accrington Carpet & Bed centre on Blackburn Rd near Antley. I am not sure whether they are still in business because they had a bad fire less than a year ago (other forum members wil know)
John West carpets on Moscow Mill St opposite the Ossy Mills car park.
Both these have a carpet fitting service if you need it.
Winfields used to sell carpets but I have never bought there, may still sell them.
No doubt other member here will know of more retailers - you will be spoilt for choice