The Food Safety Act 1990 was amended by EU legislation in 2004 by Regulation (EC) No. 852/2004 on the hygiene of foodstuffs, Article 6(2)), with regard to registration of food business establishments:-
'In particular, every food business operator shall notify the appropriate competent authority, in the manner that the latter requires, of each establishment under its control that carries out any of the stages of production, processing and distribution of food, with a view to the registration of each such establishment. Food business operators shall also ensure that the competent authority always has up-to-date information on establishments, including by notifying any significant change in activities and any closure of an existing establishment.'
The section in the FSA 1990 Guidance quoted as below has been superseded and no longer applies, although still available to view.
"The registration requirement does not apply to certain premises, which are not used for more than a few days or are not used regularly. Registration is required if premises are used for the purpose of a food business for 5 or more days (whether consecutive or not) in any 5 consecutive weeks. This rule also applies to any premises used by two or more food businesses."
FSA Code of Practice (England) and is now taken into account
Further information on the changes can be found at:
http://www.food.gov.uk/enforcement/enfo ... egislation
They seem quite willing to discuss the implications and the need for registration during an inspection/advice visit.