I have used cadence sport for a fit, I had the £150 one (i think "Endoman" has written a report in the reviews section - worth a read).
Some people are of the opinion that its too much for "some bloke to move your saddle"
But the way I look at is I have brought a bike, I want to ride it in comfort and I wanted someone that knows to make sure I wasnt in a position that was going to cause problems.
You have to look at it not only as getiing your bike fitted, but the information you pick up too. Now I know my previous mistakes and I know how a bike should feel I probably wont need another fit unless I changed bike discipline, such as doing TT (and with my belly, that aint likely)
Before the fit I could do 30 or so miles then pins and needles in hands and feet set in, but worst of all was the achy shoulders and neck. By 40 miles I would be getting really fed up.
I did the flat out in the fens and didnt really start getting any real discomfort untill about 90 miles, that said, I did it with a friend that was slower than me so I was out of my optimal position. If I were riding at my normal pace I know I could have been more comfortable for longer.
After the fit I felt less powerful on the bike, though my average speed tayed the same. I had been in the wrong position and not using all my leg muscles so after the fit I had to adapt. Now I feel more muscle being used and I can hold I higher speed for longer, also feel like I am pedelling better and not just mashing down on the pedels. With the tips Ada gave me my shoulders and neck dont ache, also the hand dont get pins and needles any more. And the footbeds make my shoes more comfortable.
I guess you could watch youtube, and read different articals and you might get lucky and get a ggod fit. Im still happy I went and spent!
TIPS: Make sure you get there in time, but not too early or you will be drooling over pinarellos and assos gear.
Make sure your bike is clean, probably best not to go the day after a wet sportive on cowsh!t covered roads.
Make sure your shoes are clean as ada will be adjusting your cleats. (also make sur the bolts can be loosend)