Photo Express did a roll of cut negatives and a roll of transparency strips for me for the base price and the result was excellent. If you've got mounted slides the price might go up. At one point I was looking at places like "Treasured Memories" that do this sort of stuff; for quantity the price per unit goes down, but the total bill goes up and up. I bit the bullet and got my own scanner (then sent it back and got a proper one!). Saved a bucket and enjoyed the process, too (which not everyone does, for that sort of quantity). The thing for me was, I'd forgotten a lot of stuff, and going through the slide boxes and neg envelopes sorting them out for scanning and then seeing them come alive, really brought things back to me. I still remember the feeling when I saw my Australian friend, met over there, standing braced against the wind on the Quantocks, hair streaming, must have been in the early 70s. I'd completely forgotten that he'd come down to visit my parents at a time I was home from Oz too. I think you miss some of that sort of feeling if they're done elsewhere and you only get to see the results, in the same random order as sent.
(ETA: worth asking if Photo Express will give you the 50p per film discount off scanning that they do off process and scan...)
