It seems like the stud wall I'd planned to remove to make an open plan lounge/kitchen in my 30 yr old house is not the frame structure I'd expected.  I removed a bit of the dry wall on one side to find the top plate but there's no top plate - just a gap between the dry wall either side of the frame that seems to continue up into a 1st floor wall that is above maybe half of the width of the ground floor wall. About a third of the width of the ground floor wall then runs under the staircase.  I want to remove the whole ground floor wall and if it was a regular stud frame wall I would have done so but now I'm concerned it may be an issue because I don't recognise this design??  

It surely can't be a load bearing wall - it runs parallel to the ceiling joists above and as mentioned the stairs are over about a third of the wall (and it has a doorway in the middle of it).  The survey mentioned standard stud walls and didn't comment that any were load bearing.  Does this sound like I can safely remove it and block up/plaster the gap??!  Is it a standard design for a non load bearing stud wall?  
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  [1]: https://i.sstatic.net/N0cBk.jpg
  [2]: https://i.sstatic.net/AHzDG.jpg