Sidereal time offset

The offset of sidereal time from UK civil time increases by 2 hours every month, but is disturbed by summer time. Assuming that the clocks go forward on Mar 28 and back on Oct 28, and that the offset is closest to an integer number of hours on the 6th and 22nd of each month, then the crucial points to remember are

March +11 and +12 (On Mar 22 Sun has RA 0h and is 0 hours from culmination at 1200)
April +12 and +13 (April fools you by repeating 12)
October +0 and +1 (October)
November +3 and +4 (November skips over 2)

People are asking me what I mean by 'sidereal time offset'. The idea is to have a quick way of working out the approximate current sidereal time in my head. The sidereal time offset is the number of hours you add to the civil time to get the sidereal time.
For example, at the spring equinox sidereal time is 12 hours ahead of UK civil time (GMT in this case) so the sidereal time offset is +12 - if it's 11am, then the sidereal time is 2300.
Similarly, at the autumn equinox sidereal time is 1 hour behind UK civil time (BST) - the Sun has RA 12h and is 0 hours from culmination at 1pm BST (1300), so the offset is -1 (or +23 if you like). Remember, when BST is in force then the sun isn't due south at noon, because noon is actually only 11am.
(Yes, I know about the equation of time but its maximum effect is a variation of 18 minutes, which we can easily afford to neglect when making an approximation).

All right, you've talked me into it, you can have a table. I've emboldened the points where the pattern is disrupted by UK daylight savings time. US DST starts a month later in the spring IIRC.

Month	Offset 6th (h)	Offset 22nd (h)
January	+7	+8
February	+9	+10
March	+11	+12
April	+12	+13
May	+14	+15
June	+16	+17
July	+18	+19
August	+20	+21
September	+22	+23
October	+0	+1
November	+3	+4
December	+5	+6

Or to put it another way:

Sidereal time is civil time...		Sidereal time is civil time...
+0	Oct 6	+0
+1	Oct 22	-23
+2	-	-22
+3	Nov 6	-21
+4	Nov 22	-20
+5	Dec 6	-19
+6	Dec 22	-18
+7	Jan 6	-17
+8	Jan 22	-16
+9	Feb 6	-15
+10	Feb 22	-14
+11	Mar 6	-13
+12	Mar 22, Apr 6	-12
+13	Apr 22	-11
+14	May 6	-10
+15	May 22	-9
+16	Jun 6	-8
+17	Jun 22	-7
+18	Jul 6	-6
+19	Jul 22	-5
+20	Aug 6	-4
+21	Aug 22	-3
+22	Sep 6	-2
+23	Sep 22	-1