Time Expired Pyrotechnics (TEPs) or distress flares as we tend to refer to them are explosives and, as such, UK laws are strict on their disposal. In the past individuals with British registered vessels could rely upon HM Coastguard to take time expired flares but nowadays this service is less likely to be offered.
Some marinas. life raft service stations, police stations or fire stations may take them, as may some Coastguard Stations although they are not obliged to do so. Never turn up without prior arrangement. There are also periodic flare amnesties.
Some Local Authorities can deal with hazardous goods (as opposed to hazardous waste) although there is likely to be a charge. Commercial organisations will almost certainly be charged for disposal.
It is worth considering whether the original supplier will take out of date flares as part of a ‘take-back scheme’ although this is probably best checked at date of purchase! You might also want to consider when the next flare amnesty may be run by Ramora.
Contact HM Coastguard when all other means of disposal have been exhausted.
There are regulations relating to storage and transport but private individuals in the UK can transport flares relatively unhindered. That said, flares can kill and so sensible precautions should be taken when storing, transporting and disposing of them. It is a criminal offence in the UK to discharge, dispose of at sea or otherwise illegally dispose of flares in an improper manner.