I've also heard good things about the Cosina Voigtlander 90mm f:3.5, which carries an 'apo' designation. It is also a screw mount, and would need the adapter to mount on the M7. The Cosina Voigtlander lenses are available from cameraquest.com and photovillage.com. I don't use a CV 90mm because I've got a Leitz-made Rokkor-M 90mm f:4 and a Minolta M-Rokkor 90mm f:4 (inherited the second one). Most practicing photographers think the Leica warning about using the lenses for the CL on the M series was a ploy not to have the CL take away market share from the much more expensive M5. A lot of people do it, and I've never seen anyone report problems. Last time I looked the Minolta and Leica lenses for the CL/CLE were going used from US$250 to US$300 for a good sample.

Another lens I do have, and would highly recommend if you could use something just a little shorter and a little faster, is the Cosina Voigtlander 75mm f:2.5 Color Heliar. I personally like the focal length a lot, and have used it for shooting indoor soccer, wide-field astrophotos, candid portraits, and scenery. The astrophotos show pinpoint stars to the corners at f:2.5, and I'm very impressed. If you're worried about boke (bokeh), the out of focus highlights are smooth and not at all distracting. Contrast is excellent (but not to current Leica standards), and I can see a little flare when shooting directly into the sun. The price is about US$300, and you'd need the thread mount to M adapter for this lens as well. I don't know a European vendor, but I suspect prices would be a good bit higher there.

I have also seen the warnings about the Jupiter 9 focusing and other problems on the M cameras that Denis P. mentions.

Best of luck,