A lot of people use our 0800 number but, to be honest, its very difficult to try to evaluate whether people would still have called if they only had our normal phone number to use. We assume that the customer appreciates they can call to get free advice which is truly free.
For others, a lot of it depends on the type of customers you are dealing with as a freephone number is more appealing to a consumer rather than a business user who doesnt directly pay for the call themselves. I do think theres a downside to 0800 numbers as people cant immediately tell where you're based which may affect those customers who are looking for a local company.
There are other options such as local rate numbers (0845) and a whole load of other new numbers that are subsidised in one way or another. The only problem with having so many other prefixes is that I dont think people are entirely sure what the costs are any more - it was simple when there was just 0800 which was free and 0891 which everyone knew was going to cost at least 60p per minute.
One thing I wouldnt do is promote a mobile number as these are now getting prefix numbers which are similar to premium rate and again I think there is a possibility of confusing customers.
In summary, I'd recommend a nationwide company (or at least one that covers a large area) to go for an 0800 and for those contract cleaners and window cleaners who only target local customers I'd just use the normal landline number and use the local angle to attract those customers who really want to support a local supplier. Besides, if people know you havent got to travel far they'll assume that you'll have lower costs and won't charge as much - which probably isn't far from the truth for most companies!
Regards
Mike