I can’t download an app I own

If you have followed all the steps and instructions in Related Article: If there's an issue when you redownload apps, movies, or other content from Apple and if you still need help, get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK) 

can I get a refund if they are not on the store any more?

You can only submit a refund within 90 days of purchase.

You can always try but don't expect too much, see ->  Request a refund for apps or content that you bought from Apple.

Request a refund for apps or content you've bought from Apple – Apple Support (UK)

If you have requested a refund, you must wait until Apple has approved. Then you will receive a message from Apple.

Refunds are not guaranteed. For more information, see the Terms & Conditions.

If an app has been removed from the App Store, you can no longer download and/or update it.

I also have some paid & free apps here, and those apps have been removed from the App Store.

Sometimes an app is removed from the App Store because the developer has stopped updating, or for other reasons.