The law of abstinence applies to all Fridays except when that Friday is also a 'solemnity' (i.e. a particular type of feast day) (Canon 1251). On such solemnities our Faith calls on us to celebrate in a manner that supersedes the usual call to Friday penance. In England and Wales the following are solemnities and if they fall on a Friday in any particular year then they supersede the Friday absence law:
Jan 1 (Mother of God),
March 19 (St Joseph),
March 25 (Annunciation),
April 23 (St George),
The Friday in the Octave of Easter (i.e. the Friday following Easter),
Sacred Heart (the Friday following Corpus Christi Sunday)
June 24 (St John the Baptist),
June 29 (St Peter & St Paul),
Aug 15 (Assumption),
Nov 1 (All Saints),
Dec 8 (Immaculate Conception),
Dec 25 (Christmas),
& the Friday in the octave of Christmas (i.e. the Friday following Christmas).
In addition, there are local solemnities that would hold in a specific diocese for the people in that diocese, for example, June 5th in the Diocese of Plymouth is the Solemnity of St Boniface, our patron.
A spokesperson for the Bishops' Conference of England & Wales made the clarification about Fridays in the Christmas Octave in December 2014, saying that it is “contrary to the mentality of what an octave is to consider one of its days as penitential.”