No, I've not served s.21.
The tenant moved in on 15 October 2013 (rent payable in advance on the 15th of each month). They paid again on 15 November but not on 15 December, January or February.
My understanding is you can't serve s.21 in first six months of a tenancy but you can serve s.8.
I've used the correct s.8 notice of possession form but my concern is that not waiting 14 days to start the PCOL may harm my case in court.
I also have grounds for s.14 (anti-social behaviour) but don't want to use these unless necessary to prevent aggro for their neighbours (who have provided me evidence).
Thanks for the advice. I will withdraw the application and start a new one in two weeks.