Could I just add my ten penn'orth to the previous posts and say that you can get a decent scanner for around £60-£80 these days and most will cope with slide negatives and positives. It's a bit fiddly at first but, after you've done a few, it's not too irksome. At 50p a slide - worst case from your quote - £60 buys you more than 120 slides because you get to keep the scanner!