Ceiling height : garage conversion knocked through to lounge

[VioletG]

Hi,

Our garage was converted to a small room and bathroom a few years ago, it sits next to a lounge and we want to remove the wall between the garage conversion and existing lounge to make one big lounge and add a window at the front (where a faux garage door currently sits).

Issues:

The garage is a pitched roof but the front is lower than the existing house. So adding a new window currently would be a different height to the other front windows.

2. The ceiling in the garage conversion would be a different height from the existing lounge. So when we knock it through there would be a noticable difference. Ideally I want it to be the same height so it looks like one room.

We have planning permission to do the above. One builder says its not possible to achieve and another says it is.

I just wondered what our options were. Would we have to rebuild the garage?

Thanks

[big-all]

wow that one heck off an expensive bit off engineering assuming its the external house wall and a wide opening far far more expensive than an internal wall