Thanks for replies
We found the solution after realising that we did not need to include AS in the code. Also, as pepperstreet pointed out, CONCAT only needed two arguments. Fortunately the client only wanted a mean average. So in case this helps others, here is the final code we used, and it works perfectly...
SELECT CONCAT(DATE_FORMAT(FROM_UNIXTIME(date_submitted),'%d/%m/%Y'),' - ',(ROUND(((score_a+score_b+score_c+score_d+score_e+score_f+score_g)/7),2)))
FROM rms_ind_scores
WHERE username = {USERID} AND rms_ind_scores.storeid IN (SELECT DISTINCT store_id FROM rms_users LEFT JOIN rms_user_usergroup_map ON rms_users.id = rms_user_usergroup_map.user_id LEFT JOIN rms_clients ON rms_user_usergroup_map.group_id = rms_clients.usergroups_id LEFT JOIN rms_stores ON rms_clients.client_id = rms_stores.client_id WHERE rms_user_usergroup_map.user_id = {VIEWERID} AND store_id IS NOT NULL)
ORDER BY date_submitted DESC
LIMIT 0, 3
Thanks for the help