You could look at using one of the nematode worm slug killers such as
described at

http://www.greengardener.co.uk/slug.htm

The RHS site mentions nematode worms too

http://www.rhs.org.uk/advice/profiles0700/slugs.asp

Shop around the net - or look at a garden centre - they will sell the
nematodes as a card you post off - you then receive the packet of live
powder direct from the supplier.

HTH

Noz

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I'd rather you replied here though. Thanks.