How did you do it - did you get a quote from Howdens, or a fitter who uses Howdens?
I know I've said this several times before, but go for the latter and get quotes from different fitters, and make sure that they know they are in a competitive tender.
Howdens give their trade customers a huge discount, so a decent fitter will be able to get you anything up for 50% of the non-trade list price, and are more likely to pass more of this on to you if they are competing with others for the job.
Also, research and buy your appliances separately. Depending on your fitter's suppliers, they may be able to get them cheaper than you buy them direct. Don't get them through Howdens.