Lunn Poly are part of the 'World of TUI' which owns a number of different tour operators - these include Thomson, Crystal & Simply Travel. They will of course try and push their own branded holidays over competitors as they would normally get a better commission rate for selling them. However if they haven't got anything available for your requirements they will of course look at other companies.
Have you tried looking on - www.travelsupermarket.com - here you are able to do a price comparison to find the cheapest holiday/hotel/flight etc.