I would’ve preferred a full refund too, but as my tickets were purchased as part of a rail staff concession, I had to take the evoucher option. They took about two days to process the request via the online form, but they have not responded to any requests with regards to whether or not I can actually use the evouchers to book the same concession ticket (I have to book our tickets via a different site, run by Eurostar, and where their own staff are also able to purchase tickets), and this is partly why I wanted the refund.
Just an aside (in relation to other transport tickets I have been trying to get refunds on): As the Eurostar journey was supposed to take place on the 18th April, I had to give up waiting and just filled out the evoucher request form. The Eurostar leg of my journey was the first leg of an actual Interrail trip to Italy.
I was able to get a full refund from the UK/ATOC distributor of Interrail passes with zero issues, though they are now starting to offer vouchers instead and whether or not you get a full refund depends on when you actually ordered your Interrail pass and the planned start date.
Using Monzo, I had also booked mandatory seat reservations through ItaliaRail, and they were initially offering 80% refunds as well as coupons but told us not to contact them and it would be sorted/we would be contacted directly. This hasn’t happened, so I’m not sure what to do next. Still also trying to claw a refund or something out of Alitalia for flights from Rome back to London (also booked with Monzo), but I’'m on the verge of giving up.