Looks like I also have a collar to stop me sinking further into shit!

Thanks for the heads up 'dog... sort of... looks like a handy solid piece of kit and for the price, I wouldn't mind giving them a try, however, I fear that international shipping might dampen that druther.

Similar to MrR', but mine is a set of these ring depth stops that cover a large range of sizes in smaller increments,

No idea where I bought them, however, they are not LV, as that is too far away, and I do know I paid for them in some dodgy shop.  They were upgraded by these less wood marking sets,

which cover a fair range from very small to not so very small.  Both the above sets don't mark the work if I remember to use a credit card before I start drilling... and it's always better when I don't use a current card.

For larger gauges, I use this Incra jig for the depth stop,

One of the columns has a tapered groove down it so that the stop collar wont move, even if you bottom out,  aggressively.... and I also need to justify the shekel magnitude of the jig.

Occasionally I precisely set up a drill with some masking tape,

which will clear the sawdust off the workpiece as a second indicator when you've reached the appropriate depth. I find it invaluable when I drill in the ceiling and don't wan to look up and see when I reach the depth because of the debris falling down into my eyes, potentially blinding me... gummed up eyes is not recommended for descending a ladder.

FAIW, I was blindsided when both my batteries eventually died for this Triton drill and no cost affective replacement. It had a magnificent built in depth stop,

and served me well even with the Ryobi battery hack, until it was made redundant with the  above mentioned Woodpecker jig, though it cost me a lot of shekels and extra setup time.
 

If your first cut is too short... Take the second cut from the longer end... LBD