AOPA
Apparently AOPA teach and examine in PPL theory see abstract below from their site but they are not, as far as I know an ATO
PPL Ground School available in Central London.
Following the popularity of our courses, AOPA are pleased to advise that a further evening programme of PPL Ground School will be run at our Central London offices.
Starting on 4 October 2016, AOPA will be running ground school for ab-initio pilots. The School will take place at the AOPA offices at 50a Cambridge Street in Victoria and will take place each Tuesday and Thursday evening from 7 till 9pm on the dates shown below. The AOPA office is just 5 minutes walk from Victoria Station.
All 9 subjects required for the PPL (aeroplanes), will be taught over a period of approximately 70 hours. The lecturer is Adam Winter, a highly qualified and experienced flying instructor who works for the Flyers Flying School at Elstree.
CLICK HERE FOR MORE DETAILS
The next programme for 2016/17 is:
Air Law October 4, 6, 11, 13
Operations and Procedures October 18, 20
Human Performance and Limitations October 25, 27
Revision November 1
Exams November 3
Navigation November 8, 10, 15, 17, 22, 24
Meteorology November 29 December 1, 6, 8, 13, 15
Revision December 20
Exams December 22