I'd like to share my experience with PEO Croydon , went on the first week of July for Set M (spouse)
we wasnt informed of any problems with the system until we were at the first window past the security,...at this point we were informed that they have problems with their system and we will not received our decison today and we could cancel our appointment if we wanted to??? as if we got a choice ???
so we went upstairs, payment made registered in system, biometrics done, went to window and check all documents , back to window to submit all documents and was told they cannot process my application and will receive a phone call for the decision on my application because the system finally crashed ... feeling so disappointed and also a bit fobbed off at travelling all that distance to a crummy place like Croydon, paying all that money for a premium service but did receive a heartwarming 2nd class service!!!

Anyway, after a long and anxious wait of seven days I received all my documents via recorded post (Royal Mail) with my passport and a letter saying that my application was approved , the BRP is also on its way as I missed a different courier for that yesterday !!

Heres how I arranged my documents (note: no staples / no paperclips..separate the originals and photocopies of each)

Scanned copies of all the passports
Marriage certificate
3 months bank statements (both husband and I)
Payslips (both husband and I)
P60 (both husband and I)
KOL notification letter
Cohabitation letters both husband and I for 2years (note: we just submitted from 3 different sources)

hope this helps and goodluck to all the future applicants and all those who are waiting. Happy Days!!