Agree with Vahe. Also, warnings are not necessarily errors but meant to raise flags for you to check the site to see if everything is meant to be there.
An incorrect rollout of canonicals (e.g. if every page on your site has the home page as the canonical) can result in a lot of pages being removed out of the index.
Regarding the 301s, check all pages for links to other internal pages & look at any links that have a trailing slash at the end and change to remove the trailing slash, e.g. these are 2 different URLs:
- http://www.musicliveuk.com/category/planning-events
- http://www.musicliveuk.com/category/planning-events/
Yet "/category/planning-events/" 301s to "/category/planning-events"
The non www version 301s to the www version too.. so check if there are any internal links to:
and change to:

