Yes, 20yrs front date of file for patent (I am very familiar with patent and patenting process).
The "copyright" in this instance would be treated like a US Design patent or a trademark mark. Again, after more than 30 years, I cannot see how it was defendable and as mentioned the EU court rules against it...
As far as I am concerned, it was a waste of money but it could have been strategic like people running "patent pending"; during the court case, competitor may refrain selling things allowing Brompton to "keep/secure" some market shares and these revenues may be greater than the legal cost...
But Although companies do that, this is speculative in this specific case.