People who had already changed their IPS tag to ENOM have had their domains stuck in limbo for around 3 months with Namecheap not able to accept the transfer, ENOM themselves not able to see the domain and previous registrars not able to reverse the process. This meant applying to Nominet for the IPS tag to be changed to something else which attracted a fee of £12 (inc. VAT).
If you're still stuck in limbo you can live chat with Nominet and explain the issue as they have allowed me to change IPS tags gratis due to the issue with ENOM / Namecheap.
Although this isn't Namecheap's fault and is an issue with ENOM's bodged effort to comply with GDPR, their support and handling of the situation has been worse than awful. I went as far as calling ENOM directly and while they couldn't fix the issue, they at the least explained what the issue was and most importantly WHY Namecheap nor themselves could accept transfers of domains.