Listing posts grouped by meta_key from usermeta table

I’m designing a photography contest website. The configuration is this:

• Each participant is member of a club, so in the usermeta table every user has a ‘club’ metakey with the name of the club as meta_value.
• Each participant uploads an image (with a custom post type) which is given a score. This score is a custom field saved in the postmeta table with a ‘score’ meta_key and the number scored as a meta_value.

So, what I’m trying to do with no success is to make a list:

• with the clubs ordered ascendent alphabetically
• inside the club with the 5 best scored images from members of this club ordered descendent by score

Something like this example:

Club AAAAA

• Image 1 – 20 points
• Image 2 – 19 points
• (…)
• Image 5 – 13 points

Club BBBBB

• Image 1 – 20 points
• Image 2 – 19 points
• (…)
• Image 5 – 13 points

I hope I have been able to explain.
Thanks for your help.
álex.