Does anyone know of a duet (2 violins or violin and viola) which would be suitable for a wedding ceremony? nothing too clichéd like Pachelbel's canon, but preferably something slow and pretty. We would only have 3 weeks to learn it, so it's probably best to stick to around grade 5, or 6 at a push, and not too long.
Thanks.

You could try Wedding Music for Two Violins by Scott Sadie. It does have Pachelbel's Canon in it (a nice arrangement) but lots of other pieces too that you might find suitable. Roughly Grade 4-5.

I have a book published by UE which has violin duet arrangements of Mozart opera arias. That would work well if you can find it. Might be out of print now though as it's older than I am but worth asking around.