A lot of people who don't know much about photography will tell you all about the latest and greatest computer designed, multi coated modern lenses, but you really can't beat an old uncoated MF lens in my book, both for colour and B&W. Around my place, the older the lens, the better the photos. The IQ is just so much better on the old lenses. I could show you photos from a Voigtlander Brilliant I once owned w/ an uncoated Heliar lens that blew a Hasselblad out of the water for 3-D imaging and overall better IQ. Never should have sold that camera.
You could come up w/ a lot of work arounds (photograph the slide w/ a DSLR on a light box for instance), but the cheapest and best way to go for great results is to look for an old Epson 2450 flatbed scanner. They were state of tha art technology in their day, and still make really, really good scans w/ 120 film. I used mine w/ 35mm even and got wonderful results. You don't need any fancy film holders or software either, just lay the slide on the bed and use the Epson scanning software. These things go for $25-$40 here in the US.
You can scan negs up to 4x5, and large prints too. The only caveat is that you may have to have Windows XP or something similar installed to make use of the software. I am not 100% sure the later operating systems are compatible. You could always buy a cheap PC just for scanning, or use the XP on a dual drive HD. You have a classic camera w/ a good lens and you're shooting 120 film, may as well get some high quality results.