The descent to FL340 is due to the RAD rule EGLF1045 (Annex 2B) , that forbid south coast UK arrival to offload Brest upper sector during summer. So you can use any even level before MANAK.
But here are 2 remarks on your FPL:
The correct routing into LFRR would be MANAK UT183 BAGAD DCT MUREL DCT NOZHU and to reflect the IRL LoA between LFRR and EGTT, I would add a step descent FL300 at MUREL in order to be over NOZHU FL300. This would give you a better fuel prediction