Yeah a slapper is someone who puts it about.
Few more
Divvy - a stupid or not so bright person
Meff - Someone who dresses scruffily
Minty - dirty/unclean
Slummy - loose change (money)
Abar - about
Yewoh - (you what?)
Keep dixie - keep a look out
Sag off - stay off school without permission
Plazzy - Plastic
Bin lid - kid/child