T-SQL (SS2K8) :: Aggregate Monthly Values From Interval Values?

I want to aggregate to monthly values for the reading. I want to display Reading value for Oct 2010, November 2010 likewise My question is simple and I have tried to follow the etiquette.

Currently it is displaying.....

MeterIDReadingdateReading
3969 22/10/2013 0:150
3969 22/10/2013 0:300
3969 22/10/2013 0:450
3969 22/10/2013 1:000
3969 22/10/2013 1:150
3969 22/10/2013 1:300
3969 22/10/2013 1:450
3969 22/10/2013 2:001
3969 22/10/2013 2:150
MeterId int
ReadingDate datetime
Reading real

-===== If the test table already exists, drop it

IF OBJECT_ID('TempDB..#mytable','U') IS NOT NULL
DROP TABLE #mytable

--===== Create the test table with

CREATE TABLE #mytable
(
meterID INT PRIMARY KEY,
Readingdate DATETIME,
reading real
)

--===== Setup any special required conditions especially where dates are concerned

SET DATEFORMAT DMY
SELECT '4','Oct 17 2013 12:00AM','5.1709' UNION ALL
SELECT '4','Oct 17 2013 12:15AM','5.5319' UNION ALL
SELECT '4','Nov 17 2013 12:00AM','5.5793' UNION ALL
SELECT '4','Nov 17 2013 14:00AM','5.2471' UNION ALL
SELECT '5','Nov 17 2013 12:00AM','5.1177' UNION ALL
SELECT '5','Nov 17 2013 14:00AM','5.5510' UNION ALL
SELECT '5','Dec 17 2013 15:00AM','5.5128', UNION ALL
SELECT '5','Dec 17 2013 16:00AM','5.5758' UNION ALL

Output should display as

MeterId Period Reading

4 Oct 13 10.20
4 Nov 13 10.40
5 Oct 13 10.20
5 Nov 13 10.40
4 Dec 13 11.15