At the moment my sites are taking a long time to load or often not at all. Cloudflare says that my origin server is not available yet if I enable developer mode in the caching options my sites load fine.
Since you mentioned you tried clearing your Cloudflare cache from your hosting provider’s dashboard, yours seems to be a Cloudflare “partner setup”, where a partner (hosting company) provides and charges for Cloudflare services. In a partner setup, your DNS is typically pointed to your hosting provider with a special CNAME configuration.
You should insist with your hosting provider that they offer you a solution. You may also want to share both your domain name and the name of your provider in the hope some volunteer here in the community may have a similar setup and perhaps a tip or two on how to deal with your problem.
Alternatively, you may want to remove your domain from Cloudflare via your hosting partner, and re-add it directly on Cloudflare’s dashboard, to have fuller control of Cloudflare services. But you should only do so after comparing your provider’s prices (if any) to those of Cloudflare, as plans and prices do vary.
As for the problem itself, just saying images are not caching/loading properly, or are taking too long to load, is not enough to qualify the issue. Please provide your domain name and be more specific as to what errors you may be seeing.