Despite retrying the same process several times, I removed the TDE, certificate and master keys across all instances and started from scratch with the exception of re-backing up the database. Despite all passwords and certificate names being the same still no joy.
I then removed the TDE, certificate and master keys across all instances, restarted both instances, then created a master key, then the cert, reapplied the TDE, then carried out all new full, differential and transaction log backups all on instance one. Backup up the certificate from instance one, then on instance two created the same master key, imported the backup up certificate from instance one and then carried out the database restore and all is well.
None of my T-SQL changed in any way, the only think I can gather is some sort of security failed to correctly apply, maybe a tempdb issue.
I have read others having the same issues, I hope this helps others.