Depends on a lot of factors but a trickle charger might only draw up to a few amps so in principle you could do it. Would be better to test the circuit but that would require access to the source cu, should also have an rcd somewhere but that's only if you are playing by the rules. Maybe use a lighting socket (small round pins low amp rating), normally used for table lamps. That would stop you or anyone else plugging a high current 13amp item in and wouldn't look so out of place on a lighting circuit.
Depends on a lot of factors but a trickle charger might only draw up to a few amps so in principle you could do it. Would be better to test the circuit but that would require access to the source cu, should also have an rcd somewhere but that's only if you are playing by the rules. Maybe use a lighting socket (small round pins low amp rating), normally used for table lamps. That would stop you or anyone else plugging a high current 13amp item in and wouldn't look so out of place on a lighting circuit.