I've reverted to the previous code by grevious trial and error and copying of older code. Anyway I got it done last night.
I then modified the blocking code so it will work over boundary breaks. I also fiddled with the class structure. I'm pretty happy with the progress. Tonight I'll attempt to add map object blocking as well - it seems to have dissapeared for some reason. Then I'll add map object blocking over boundaries - if this doesn't happen automagically.