philjo, I used to use a USB plug in 35mm scanner and was semi happy with the results.
Due to shooting allot of 35mm and 120mm film I recently upgraded to an Epson V600, I got it 2nd hand from eBay for just over £150. The scanner itself its a little larger than I had wanted and depending on the settings you choose can take a while to complete each scan, but the output quality is superb. The software included is also very clever and can remove dust, scratches and when scanning older slides/negatives it enhances the colours so the results look like new.
Before buying the V600, I had read allot of good reviews about the V500 which can be picked up for a reasonable price too.