I had the same problem Stuart
When i first got Taz (RIP) the whole safety collar thing wasnt as high profile (nor was microchipping cats) or well known and i got him a normal type (my Nan used the normal buckle type with no issues at all - probably 2 losses out of 30 odd cats over the years) I proudly got his disk and off he set into the world.
1 day. Gone. So it was replaced, new disk, posh as toffee.
1 week, gone.
It started where i gave up with disks and permanent markered the collars. Then obviously the safety collars when they appeared. Then he'd go periods with no collar at all, then others where the collar remained for a year or so.
Nuggie was the same. He is currently collarless, but his last collar lasted over a year and went missing just at the point i thought "ooh hes done well with that collar" ....
Peanut lost his reflective collar after a month, which is a long time lol i replaced it straight away incase it was removed by someone to check owner ship. Hes done well and hes had that 8mths
Evie got a collar all lovely and pink and it didn last an hour. We found it today though and its currently "drying out" on the radiator.
I got a collar for her (safety) - unsure of make and she nearly choked. I'll post a pic of how i found her (Please Note: this is a reinactment photo with the help of a trusty teddy - I didnt take a photo before saving her
lol) but i think it had caught, pulled tight but she didnt pull hard enough for it to release
Anyway, i think like you an endless supply of collars is probably the only way
pic to follow....