depends on you :)

The standard refund is 85% of the pass value
By paying the 19€you upgrade to 100% refund.

The 10€ extra for the paperpass are the shippment cost and are not related to the refund options.

Please note with a paper pass you have to select the starting date of validity already at the purchasing process (as this will be printed on the paper ticket) with the mobile pass you can select within the 11months flexible when you wanna start.

The £19 "free cancellation” is only useful when you ask for a refund for your Interrail pass. Then you'll get a 100% refund instead of 85%. I've never taken it; I find it a bit expensive...

You can always activate your pass within 11 months after purchase.

The paper pass costs an extra £19 for delivery costs.

The £10 pass protection for a paper pass does not cover refund (which is 85% before the first day of validity). For the refund and exchange policy, check this page.

You may also want to check www.myinterrail.co.uk (run by National Rail / RDG), where the prices in GBP seem to be slightly lower and delivery cost for a paper pass is £10.

Great thank you! So if I were to buy a mobile pass without the extra £19 cancellation fee I’d still be able to activate it within 11 months of buying? 

Sure! That's a basic functionality of the mobile pass.