you would need a catnic lintel and the only way soldiers would dip in the brickwork if it was a really big span and wasnt clipped in correctly and weight is pushing down
Cavity Wall Lintels for Traditional house fixed to inerleaf
timberframe lintels for timberframe houses which should have clips to fix lintels to timber frame
dont kinow price or a builder wouldnt till seen the job !!!!

hope this is of a help

time served bricklayer and roughcaster

It is entirely possible that the original Brick lintel is more than sufficient to support the wall above, Was it arched upwards to the centre originally? or were they straight at the bottom, but with bricks leaning outward from the centre?
If they are just straight and vertical, there is probably an existing lintel in place, but it may need relaying.

You will need to have the soldiers removed and a 6" either side of the window for angle iron to spread across. This will then need to be re-laid with bricks and soldiers.

The section would be bricklaying. Regards Steve

Your window fitter should have advised you that you needed a lintol before he fitted the new window.
Its not a 5 minute job, and will probably need some strong boys put in to hold up the brickwork, knock of the plaster and couple of course of bricks inside and hopefully slide in a catnic boot lintol, pack up tight and replaster.
Put your job in the Post a Job section, hardly likely you will get it done within 2 weeks, as most good builders are busy, and would need a bit of notice.
Cant really give a price, a lot depends on the opening size, what material is being cut out and how much plaster gets damaged.

This is not a major job, but would of been a lot easier done as/ or before new window went in, now one would need to see what type lintel would suit best, for ease of installation.Size of opening will help in giving a quote,age of property also may help
Hope this helps a little.
Regards Chris

Could be that the brickwork soldiers have "slipped" because they were built straight on the original window and would then rely on compressive strength to hold them in place.

When it was wrenched out, it probably disturbed the soldier course only. Inside would be ok as it should have a conrete lintel.

Providing the surrounding brickwork is stable you should remove all the soldier course and insert an angel iron over the new frame with a bearing of 150 mm either side and replace with new soldier course.

Note - I am guessing as it is a kitchen window it is no more than 4ft or 5 ft wide, in which case i would charge you around a days work of £120.

Hope this helped.
Regards
Pete