how to get an SP to lookup the list of institutions from the ukfederation metadata

[Sunny]

Hi,

Newbie to shibboleth and ukfederation/eduGAIN.

The IdP is fully integrated with ukfederation i.e. our IdP appears in 
metadata that is downloaded every night. I have an SP and want to use 
the ukfederation metadata so users worldwide can select their home 
institution from the drop down list which will redirect them to their 
home IdP to authenticate - I can manually get it to show the home 
institution via adding info to relying-party.xml but am not sure how to 
get the SP to lookup the ukfederation list.

Any advise, greatly appreciated.

Regards