I had exactly the same complaint a while back; the cost of processing in the UK is shocking, especially considering that no-one will give you any kind of discount for quantity, and everyone seems to do automatic colour correction (which often looks horrible). I considered having the shop develop without prints and scan onto CD from the negative, and tried it once. Never again - the resolution was so low the images even looked bad as thumbnails.
Eventually I decided to get a flatbed like the one you're looking at - the Canon equivalent anyway - and now I can't imagine trusting my prints to a high street shop again. Don't worry about how big the image will be when it's scanned - I scan at 3200dpi (the maximum
optical resolution on my scanner) and have no problem with prints up to A4 (I can probably print larger, I just haven't tried).
You do however need to keep the negs clean, and have enough time and patience to scan the negs and then clean up the scanned images. Shops don't always take very good care of your negatives, so sometimes they'll come out with small scratches or marks. These get picked up by the scanner, as do bits of dust and hair which will unavoidably get onto the film or the scanner glass. This is not really a problem, since removing the offending spot or line from the scanned image is easily done with the clone tool or something similar in Photoshop or whatever program you're using. Anyway you don't need to do this during the scanning process as you can do it when you come to print that image, since you'll want to do crops, colour/contrast correction or other alterations anyway (which is another advantage of scanning/printing your own negs over having a shop do it).
Scanning your own negs with a flatbed is a very good way to go, provided you have the following...
- Time.
- Patience.
- RAM.
- Photoshop/The Gimp/etc.
- Lots of hard drive space or recordable CDs/DVDs.
- Decent monitor.
- Good printer (or access to one).