Also you may want to seriously consider neutering them both as, as that article points out, it's waaaay harder (and in some cases virtually impossible) to fully get a dog out of this habit with all those hormones telling him to do it.
Remember and never tell them off when you catch them weeing indoors as that may make them scared of you, wee in hidden places and/or completely distrustful of humans etc.
That is a very informative link :-) its helped open my mind to other potential reasons for him doing it. Think it could possibly be the protecting his pack as Harry is the more dominant out of Harry & Bert... I've been giving him into trouble with a firm no & opening the back door to encourage him to go out. Think I will try and reinforce praise for doing the toilet outside
We had a problem with our boy marking inside the house a few months back. We kind of went a different approach than most people and got him one of the adorable doggie hydrant pee posts. We put it on a puppy pad in the house and let him mark on that. Then we slowly moved the pad and the pee post closer and closer to the door. He did pee a few other places, but we used an enzyme spray in the areas he did, that way he wouldn't smell it and want to mark there again. After a few days we moved the pad and post right outside the back door and then further and further into the yard and took away the pad. Now he marks on his hydrant all he wants and actually poops next to it too. Its his "spot." He's only peed in the house once since but that was we came home a bit too late, so that was our fault for leaving him too long. If anyone else wants to try the pee post/pee pad method this article has some good tips: www.smartdogguide.com/a-dog-fire-hydrant-potty-is-your-lawns-best-friend/ Anyway that's what worked for our pooch, hope it helps someone else.