Since I got a whole raft of sites de-indexed, has anyone got any tips on getting Yahoo results ?

You can take help from Google.

dont go on with yahoo mate.. try bouncing back with google.. google is the ultimate resource.. you ll get only less than 10% earnings/response when compared to google..

So try their guidelines and do some high quality link building and add more unique content.. tats the way to go according to me..

Seo isnt different really for yahoo. Keep building up back links and you will bounce back.