According to the latest edition of the BNF (British National Formulary), the drugs listing, prescribing guidance, etc. used by doctors and pharmacists, Thalidomide is currently unlicensed but can be given under specialist supervision. Although I appreciate that Thalidomide is rather different, it's not that unusual for unlicensed drugs to be prescribed, for example, drugs unlicensed for use in children due to the ethical problems of using children in clinical trials but licensed for use in adults are nevertheless given to children, I'm also aware of at least one other drug which was withdrawn from use in Europe and the USA being later licensed for use in the UK in only very limited circumstances, in this case for for the condition it was originally licensed for.
If you want to read more, there's not a great deal of information, the BNF website is here:
You have to register to use it; the information you might be interested in on Thalidomide can be found in Section 8.2.2 Corticosteroids and other immunosuppressants or just put thalidomide into the search engine (the other section on Thalidomide relates to treatment for leprosy for which it 's been in use for some time). I hope that this is helpful.