Okay, tried to compile an accurate list, but you'll appreciate that there are 28 seasons of league cricket here (and I'm still only 40).
I've tried to add timeframes to these, because I think there have been ebbs and flows of standard over the years - a noticeable upshift around 2007-11 as the Ashes generation came of age, and a drop off in the last couple of seasons. The eagle eyed may notice that I have rated a D3 stronger than a D2 - I stand by that. I've included one in caps that I spent a year umpiring in as I think it is indicative, as well as one that I have spent enough time watching to judge, again in caps. Apologies if I offend anyone:
North Yorkshire South Durham League D1 (mid-90s)
YORKSHIRE PREM (1997)
Northern Premier D1 (1995-6)
York Senior League D1 (early 90s)
TVCL Division 1 (2000)
HOME COUNTIES PREMIER LEAGUE (since 2004)
TVCL Division 3 (2007-11)
TVCL Division 2 (2001-2 and 2005-6)
Nidderdale League (1998-9)
TVCL Division 3 (2003-4 and 12-13)
TVCL Division 4 and occasionally lower over the years...