Very helpful thank you. It means I have been playing it wrong as my opponent in the bunker didn't op fire on me from the bunker as I was stood on top of it. Normally there is no op fire as you enter melee but I guess this is different as you are not entering the bunker hex on the first move. Is that correct?
Correct, first you enter the terrain the bunker is in and then you will enter the bunker.
How about if I use Stealth Move to enter the forest hex (which I can with my units in this situation) and then enter melee. No op fire will happen then will it so I should be safe to enter the bunker.
Yes, you can do this if you want.
If I can't use stealth move and given how dangerous it is to melee a bunker, what is the best way of clearing them out?
It depends at what tools you have at your disposal. In some scenarios you are given tanks and those are good for bunker busting.
In some other cases you'll have rocket launchers or demo charges, that can help too clear a bunker easily.
In case you only have foot soldiers then you can use the big disadvantage of most bunkers, they can fire only within a certain angle.
Than means that as long as you keep your guys outside the bunker LOS you are free to approach from behind, or the best thing you can do is to drag fire from the bunker with a decoy unit ( or sacrifice unit ) and if they fall into your trap then you can assault in close combat OR stay in the same hex as the bunker is in and fire at it with the +2 adjacency and if lucky you can shake the occupants and get them all in melee.
A good training in bunker assaulting is the scenario from Heroes of Defiance "Phoney War" where the french have to assault a bunker complex occupied by the germans.
What do you think?