The process is on this website which you may have seen already.
there is also a guide from the Treasury Solicitor’s office which is far more comprehensive.
the correct defendant is the Registrar of Companies.
You will see a sample for on page 11 of the guide.
It’s worthwhile mentioning that if ever solicitors need to restore a company, they would normally use the services of one of the specialist firms that deal with nothing else. They would rarely deal with it themselves.
Can I clarify anything for you?
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They usually advertise in the law journals.
Here are a few firms (not necessarily solicitors)
I have no experience of any of them, I just did a search on the Internet.