160knots
You asked about the regulatory information in the UK, the current regulations are in the main EASA Certification Specifications, see the link for detail.
http://www.easa.eu.int/home/certspecs_en.html
For aircraft below 5700kg, with some exceptions, the UK CAA mandates a specification which you can find on their website in:-
CAP 747 Mandatory Requirements for Airworthiness. The specific detail can be found on their website in the Publications section. Look in the publication at, quoting from memory here, the Appendices, Generic Requirement 4.
Happy reading.
