As far as I know there are no aftermarket triggers for an 08slg in the UK, unless you scour the classifieds until something comes up.
LiPS are a Custom Products dealer, so you can go through them to get something from the states, but I'm thinking that could get costly. There was a bulkbuy on the forums a while back for CP stuff through LiPS, I don't know if there'll be another one soon.
Either way, I'm in the same boat
I hate the trigger on my SLG.