Firstly, I would not advise obtaining information simply to hold on file for future use. As you know, legislation around food can change quickly, and you would be better advised to obtain up-to-date information whenever you decide to start to enter a specific market.
In terms of where to obtain that information, the obvious starting point would be through internet research, but that is easier said than done. From my past experience, regulatory issues in the USA are generally clearly covered and available to view via agencies such as the US Food and Drug Adminstration. For markets such as Russia & Japan this is likely to be more problematic.
You could also contact UK Trade & Investment, the UK govenrment agency - start by visiting their website www.ukti.gov.uk, and be sure to register, in order to get access to market information ond other content on the food & drink sector pages. You might also approach them directly, initially via your local regional office (details on the website), and ask to speak to somebody with food & drink sector knowledge.
UKTI may also direct you to one of their team based in the British Embassies / Consulates in your target market with food & drink experience. They may be able to give you information on regulatory issues, although they may charge you a fee for this service.
Finally, I would definitely suggest approaching one of the trade associations active in the food & drink sector. Many trade associations (such as the Food & Drink Exporters Association) offer export advice, and work closely with UKTI to help UK companies to enter new overseas markets. As specialists in their particular sectors, they often have a more detailed understanding of regulatory issues & other matters specific to their sectors.
The Institute of Exports can also assist in raising awareness of exporting procedures, and offer a range of training and educational courses on all aspects of international trade.