@samshltn - Sorry you’re having trouble, I’m afraid this is a pretty common Curve experience based on what I’ve seen here/experienced personally.
I can at least tell you that the money will almost certainly get back to you, although clearly not as quickly as it should. I’ve actually had a ‘lost’ refund paid to me twice, so you may even end up in profit :). I’ve always got my own issues resolved in the end, but you do need to be persistent.
For info if you do feel the need to escalate, you’d need to send a notice before action to the address listed at companies house (https://find-and-update.company-information.service.gov.uk/company/09523903). While I understand your frustration, its probably a little soon for that. OTOH, might get their attention :).
@simonjh - good point, more metrics would be required to stop Curve ‘gaming’ the system with simple ‘still working on this…’ replies. That said, a lot of complaints I see here would probably have avoided going public if Curve had made any effort to keep the complainant informed. I think we all understand things go wrong, what’s more important is how problems are resolved.