Hi Paul,
Same as as Steve have used powerburst and other harsher non-woolsafe products including ultrapac renovate with acid rinse after with great results, normally find prespray gold sprayed down hot, agitate if really bad then flush with hot acid rinse will surfice though.
Remember that wool carpets are prone to staining and wear from heavy soiling so if very bad results will be limited. Pre qualify restricted results before commencing job especially with light coloured carpets.
All the best,
Jason.