I suggest that 120mm on a 29er FS might be a bit much, so check out 100mm 29ers.. much like the Whyte M109 (as the 120mm t-129 would ‘probably’ be more bike than you need). Not sold in the cheaper ali format new anymore but they come up regularly on ebay within your budget.
SC Superlight is a good choice, if a bit under spec’d for the money (new).
2nd hand Orange Gyro’s is also well worth considering, though some owner are still trying to sell them for more than the market is willing to spend.
I watch them on ebay regularly.. they just don’t sell.. put in low offers! That’s not to say I believe them bad bikes, I think their great just overpriced.
The 29er FS world is you oyster IMO, as though you’d expect the market to be flooded with large frame for all those taller riders recommended to go 29er, the market is actually full of medium frames! Which is bloody annoying, for some-one over 6ft
ps: I know of a nice Ghost AMR 29er if you around the midlands