errrr....BARLU-KATHY is (U)B11 , not (UA25)...
Can't think why the controller would need you to be level FL200 10 before KATHY. Unless there was an overflight at FL210 routing ORTAC-MID, and the controller needed to get you under him. Radar vectors would normally suffice.
FL200 is used as a level for inbounds to theLOREL2C , and the restriction is to be level 20nm beforeMID (or at AVANT if you prefer.... yes I know AVANT is 18 DME MID, not 20).
This particular sector (S19, or HURN EAST) is an exceptionally complicated and busy piece of airspace. You should notice some changes in the near, and not so near future. One of these will be a requirement for inbounds to EGKK via the WILLO2C to be level at FL300 by FAWBO ( I would have prefered BARLU myself, but nobody asked). There will be other major changes (allegedly)
Back to the thread (or THRED haha)..
Either hit the level restriction on the nail, or be level before. Being level before a restriction is much, much better for ATC. If you are unable to make a restriction (this goes for climbs as well BTW) TELL ATC ASAP and say what you can achieve. This will help him/her enormously.
IDEAL descent profiles (except for CDAs) are soon to be a thing for the past in UK airspace. It's just too busy to give everybody exactly what they want. So start expecting EARLY descents please gentlemen (and ladies). It's really to your advantage as we can accommodate more traffic safely this way, and the alternative is more punitive flow measures.
Best rgds
BEX