Oil Filters

[YamFazFan]

Now the sump bolt magnet on the other hand may well be of better use. But have never used one myself and worry a bit about the magnet falling off in the sump

Would it be able to do any damage even if it did come off in the sump?. Not sure, but on a similar theme I had a car a while ago that had a plastic/nylon tip on the dipstick. The tube down to the sump had a couple of twists/turns in it and one day I actually heard the tip snap off way down in the tube :'(.
Went to the garage to ask them about it and they said don't worry, put a new dipstick in, it will push the broken bit into the sump where it can stay without harm because it can't get past the oil strainer pick-up. Don't know if this would apply to other cars though.