Can anyone help here. I am new to photography but seem to be running into this problem with cutting off of part of my images. When I crop using photoshop elements5 to 5inches by 7 inches and print it out at Boots, Asda or Tesco then the prints get cut off and then enlarged slightly to make up for the deficit. Now the error is only 3mm but this is everything when it comes to printing.
My research so far shows that Asda and Boots have print sizes that are 4.9inches by 6.9 inches which probably explains part of the problem but it doesn't explain why Tesco which is a genuine 5 by 7 still has the same problem.
Any help welcome.

Most probably because your file resolution does not match their printer resolution. Call and ask what their printer resolution is and make sure your file has the same resolution. You shouldn't see any enlarging.

There is nothing wrong with your image preparation. Many of the big box printers do this. I discovered it first at Costco. I found that the stores that use the Kodak system do not enlarge and crop. These include Walmart and here in Canada Loblaws.
For me the practice of upsizing and cropping is totally unacceptable and I simply won't use those processors.
Regards, Murray

Most likely you're running into a very common problem caused by the lab's machine:

"Most labs have their printers set up to increase the size of each image by 1-2%. This expands the image beyond the borders of the paper. The reason is to prevent a white strip from being printed along one or more edges if the paper is not perfectly aligned within the feed path."

From here: http://www.drycreekphoto.com/icc/using_printer_profiles.htm
(near the bottom of the page talking about cropping)

I've run into it as well and on that site they give dimensions by which you can increase the canvas size of your file to avoid the specific problem. Frankly, this is one extra step I shouldn't have to take and will not have my restoration stuff printed at the lab that did it to me before. The other lab I use hasn't caused any problems for me so I tend to stick with them.

i think they are creating bleeds for cutting puposes? maybe if you gave them a 5.25 x 7.25, or maybe even .5, they wouldnt need to blow up your image and cut.

i dont know much about printing, so excuse me if im make no sense.