iTunes is "having difficulty downloading episodes" but I am able to manually "Subscribe to Podcast". http://bbcbeeville.org/feed

You have a mixture of episodes with and without playable media in your feed. iTunes does not display episodes without playable media as you will see when you manually subscribe.

On submission, the Store checks only the top episode. As your top episode has no playable media it assumes that there is no such in the feed and rejects you.

It's not a good idea to mix them, but in any case you need to ensure that your top episode has a playable media file. Once that's done you can resubmit. You may be told that the feed has already been submitted - this is a bug in the process - the workaround for that is to change the title slightly.