RNLI won't take them - not now anyway. we had a set handed in to the fire brigade who brought them to us and it was a fun day out trying to get rid. Don't set them off under water, the smoke rises, colours the water and then goes airborne and covers your boat too. Luckily Lifeboats are orange
I think the CG also only takes them at the 3 or so official locations hence why its so difficult.
small bucket with some concrete, bag of stones, set them inside and take a ride out into the solent - splash over board, if you get my drift

a tad irresponsible but solves the issue.
