Lintels for solid walls

Contemplating ripping out the awful Crittal metal framed windows chez moi and putting some double glazed units in. The Crittals seem ideally designed for letting heat out and drafts in. However, they're in those concrete frames which act as the lintel too and many are cracked and leaking now as the metal reinforcements inside have rusted, expanded and split the frames. In any case I've seen what happens if you try and put double glazing inside the concrete frames - you end up with tiny glass area and not much light.
So the frames have to go which means new lintels above each window aperture. The walls are solid not cavity. I'm considering the easiest way is to chop out the inner row of bricks, including cutting any headers in half and put one 4.5 inch lintel in then remove the outside row and put another lintel in. That would save propping the wall with acrows to get a 9 inch lintel in but means a bit more buggering about and expense maybe.
What's the opinion on the easiest way to go. Maybe a different solution for the upstairs and downstairs as putting props in for the downstairs ones isn't such an issue.
Dave Baker - Puma Race Engines ( I'm not at all sure why women like men. We're argumentative, childish, unsociable and extremely unappealing naked. I'm quite grateful they do though.

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