Shaun,
I have just checked out your site sheffieldcleaning.com and it is very well placed if not top for a number of search terms and it is a .com. I searched carpet cleaner sheffield and I think you were top or very close to top position.
You can not improve much on that. Your site is not bad either. I think that the big problem is a genuine lack of interest in people looking to have cleaning work done. When purse strings tighten, cleaning is one of the first luxuries to go, ( yes!!! some people look on cleaning as as luxury item. )
I have just used a research tool which tells me there are less than 30 searches a month for carpetcleaningsheffield.
But the competion is not great. Only 1 adwords advertiser - SheffieldChemDry.co.uk. But there is not much point doing adwords if you are already near the top of the search engines.
CarpetCleaningSheffield.com is owned by a company called AXIS, which you probably already know. However, the website is poor and only uses a mobile phone number.
IMO I don't think you can do much more, other than enlarging your target area.
Jim