Building advise needed

[Tiger]

Do a tiger and put a couple of Acros in there. lol
you need an RSJ in there

Lol

[jmhole]

cant really tell from pictures but just to be sure thats not a party wall you want to rest the lintel in as that gets more involved. as mentioned earlier you would would have to rest the end of the lintel on the inner leaf of the cavity wall and not extend into the cavity but it would need a minimum of 150mm(6") of bearing and at the moment the wall you would rest it on is only 100mm thick.
So you would end up leaving at least 50mm of the left side of the door in place to bear the lintel.

[Pelicanbill]

cant really tell from pictures but just to be sure thats not a party wall you want to rest the lintel in as that gets more involved. as mentioned earlier you would would have to rest the end of the lintel on the inner leaf of the cavity wall and not extend into the cavity but it would need a minimum of 150mm(6") of bearing and at the moment the wall you would rest it on is only 100mm thick.
So you would end up leaving at least 50mm of the left side of the door in place to bear the lintel.

Well, that isn't strictly correct. As long as you consider what is supporting the beam, you won't have a too much trouble. A spreader of 6mmx100x250mm (running in parallel with wall) would be stacks! Just bear in mind that if you imagine a line drawn at 45 degrees / or \ then the force moves away from the point of bearing along this envelope.