At beginning of the Group created to change the characters, have another regex which will alter any entities to include '<' & '>', then also have one at end of group which removes them again.
EDIT: remove space after ';' chars (poxy smilies

)
EDIT (Jellby): no need to remove anything, you can use the [noparse] tag when posting

Before
Find: (&.{,5};)
Replace: <\1>
After
Find <(&.{,5};)>
Replace: \1