Also depends on whether it is for the purpose of public transport or not. If not, no requirement for floats. The detail is in the Heathrow section of the AIP.
Edit. No it's not, although a lot of very useful detail is. See sect 9 of the Aerodrome Textual Data.
Then...
http://www.legislation.gov.uk/uksi/2...ulation/2/made Followed by.
http://www.legislation.gov.uk/uksi/2...5/part/13/made