Usually people market on price because they don't know what else to do - and they see everyone else with coupons, so they think they will get the work by being cheap, and make it up in volume.
We always say it's better to go broke sitting on your butt in front of the TV, than to do it running a wand and working for less than it costs you to run the machine.
There is an article I wrote for Cleanfax that hits this topic exactly, called "Higher Prices, Better Clients" ... I don't know if there are parts of this that will not translate from US business to UK - but I think most of it will.
http://www.scribd.com/doc/35158272/CF-How-to-get-higher-prices-and-better-clientsI hope that hyperlink works...my first time posting one here.
Hope that gives some food for thought... we used to be 50 cent a square foot rug cleaners, and now $4-5.00 per square foot, so I know very well the changes that come from moving from a commodity cleaner "like everybody else" to becoming "the" specialist in your city.
All my best,
Lisa
