The Nagios configuration files come with a timeperiod example for US Public holidays but not for good old Blighty! Obviously that won’t do so here’s one for England & Wales (sorry Scotland!).

define timeperiod {
	name england-wales-holidays
	timeperiod_name england-wales-holidays
	alias England & Wales Holidays

	january 1 00:00-00:00	; New Years Day
	march 29 00:00-00:00	; Good Friday (Variable) 29 March good for 2013
	april 1 00:00-00:00	; Easter Monday (Variable) 1 April good for 2013
	monday 1 may 00:00-00:00	; May Day Bank Holiday (1st Monday in month)
	monday -1 may 00:00-00:00	; Spring Bank Holiday (Last Monday in month)
	monday -1 august	00:00-00:00	; Late Summer Bank Holiday
	december 25 00:00-00:00	; Public Holiday rolls forward if this falls on a Weekend (Good until 2016)
	december 26 00:00-00:00	; Public Holiday rolls forward if this falls on a Weekend (Good until 2015)
}

I never realised Scotland had such a variable system for public Holidays so have fun setting that up! Some of the holiday dates here are variable check here for details.